Muscle Car Era Engines (1964 – 1974)

What’s Changed?

The previous performance era, 1955 through 1963, had some fascinating differences from and similarities to the muscle car era proper.  In this previous era, there were several 400hp+ engines available, with 3 x 2bbl and 2 x 4bbl induction.  There was even turbocharging and supercharging!  Forced induction would be largely absent during the muscle car era, and multiple carburetors would also become scarcer.  There were only a few muscle car era engines that made what might be considered substantially more horsepower than any engine from the previous era.

Come to think of it, the Pontiac GTO itself, which heralded in the muscle car era, never made even 400 hp!  Some explanation is necessary.

Bang for the Buck!

The muscle car era was defined by one term: ‘affordable performance’.  You didn’t have to spend $4,000 (in, say, 1965 dollars) to have a sporty, quick car with a large engine.  During the previous era, performance was largely available only in a large (read ‘expensive’) vehicle, and these engines were priced at more of a premium.  We’re talking trends here, not absolutes.  A ’64 GTO with its base 389 might have a hard time keeping up with a 405hp 406cid Ford.  The GTO, though, was much more affordable than the large Ford was, and the price gap was more significant than the performance gap was.  You could sum it up with the term ‘bang for the buck’.  The ‘new’ muscle cars had this in spades!

There will be many engines that already existed at the start of this era (1964) that will be covered here, as well as engines that came into being during the Muscle Car Era itself.  We’ll look at the ‘carry-over’ engines and then the ‘new’ engines, belonging to each automaker.

I’ve thought long and hard about how to characterize the engines of this era.  There were far fewer engine-related changes during the eleven years of the Muscle Car Era than there were during the nine years of the Pre-Muscle Car Era (1955 – 1963).  Compression ratios, average engine displacements, and specific output (HP/in³) had ceased the meteoric rises of the earlier era. 

Making Them More Mainstream

Where Ford could assume the buyer of a ’62 with a 405hp dual-quad 406 was a very likely an informed buyer, this wasn’t necessarily so a few years later when performance engines became far, far more common.  In a sense, a whole swath of the performance engine list was kind of ‘dumbed down’.  Sure, the hard-core badass engines could still be had.  But we don’t want to be responsible for Aunt Florence borrowing Uncle Buddy’s 405hp fire breathing monster and accidentally getting hurt because the car was ‘too powerful’.  We’ve seen the same thing in any number of other industries, where a product is introduced for ‘the serious’, it becomes quite popular, and other more friendly competitors appear. 

Come to think of it, PCs are a good example.  They are certainly more powerful than ever, but the software and operating systems are ‘dumbed down’ to protect you from yourself!  What do you mean I can’t read this file I just created?!?!  Why, you lousy …

As a final thought, I’ll mention the ’68-era Pontiac GTO, with its 265hp 400cid V8 option, that took regular gas.  No high-octane needed here.  For the guy who wanted to look like a badass, but didn’t want to buy high-test? Uh….

Take a look at the graphs and compare them with their counterparts in the 1946 through 1963 Engine Development by Automaker section of Early US Automotive History.  This, more than anything, will illustrate the similarities and contrasts between the two eras.

1964

This year was designated as the beginning of the Muscle Car era for a couple of reasons.  The primary reason is that 1964 was the year that U.S. automakers started to focus on the segment of the market that desired performance (large engines) in smaller body styles.  Affordable performance.  The Pontiac GTO was aimed smack dab it this bullseye and was soon followed by every other automaker.  (See Muscle Cars are Like Dinosaurs or Greatest Muscle Car of all Time for more discussion on this topic)

1974

Why 1974?  By 1972, the muscle car movement was all but dead.  The onslaught of market saturation, high insurance rates, the first gasoline crisis and new federal emissions regulations had taken their toll to the point that a buyer arguably could no longer buy a new vehicle that many people would consider a muscle car.  Big engines were still around, but were emaciated by low compression, smog equipment and emissions compliance. 

But it wasn’t quite over yet.  Pontiac, the automaker who is credited with flipping the switch that started the muscle car movement in the first place, was still selling their Trans Am with an optional 455 engine that was a marvel.  Despite being low compression and complying with the current emissions regulations, this thing made 290 to 310 SAE net horsepower!  This would be in the neighborhood of 350hp+, if rated by the older gross method in place through 1971.  A Trans Am with the 455 HO engine, evolving into ‘Super Duty 455’ for ’73 and ’74, could run with the vast majority of the earlier high-compression boulevard bruisers.  This car and engine was the period at the end of the sentence for the muscle car era. (See Understanding Horsepower and Torque for information on SAE horsepower ratings)

An Overall View of the Muscle Car Era

The 1964 through 1974 era automotive market underwent continuous change in response to such factors as buyer’s desires, economic conditions, material availability, fuel quality, automotive technology, insurance industry pressures, and government regulations.  There were other factors, too, some of which came and went.  Others, like the aforementioned insurance industry pressures and government regulations, seemed to get more and more oppressive, continuing long after the muscle car era had ended.  One factor that only really came into play toward the end of the era was the influx of smaller, well-designed and well-made Japanese cars.

Muscle cars didn’t exist in a vacuum.  They were just a small part of the overall US auto market, and while lucrative, weren’t responsible for the bulk of an automaker’s profits.  To a large extent, as went the ‘mainstream’ (non-performance car) market, so went the muscle car market.  This ceased to be the case toward the very end of the ‘60’s and into the early ‘70’s, with years of great overall sales and ever declining muscle car sales.

It’s important to understand the US automotive scene in general in order to truly understand the segment of that market that is muscle cars.  Toward that end, let’s look at some relevant data.  This is the same manner in which we earlier presented in the 1946 through 1963 Engine Development by Automaker section of Early US Automotive History.

Average Horsepower

Average horsepower remained fairly constant for the first two-thirds of the era, followed by the decline of 1971 onwards.  This decline was partially ‘virtual’ and partly (very) real.  The virtual component was the change in horsepower and torque ratings from the SAE Gross method that had been used forever to the new SAE Net method (see Understanding Horsepower and Torque).

Given that the change to the SAE net method occurred at the same time as reduced compression ratios and milder cam timings, it’s not really possible to directly equate SAE net ratings with SAE gross ratings for the same engine.

Average Compression Ratios

Compression ratios started dropping in 1971, in preparation for the required unleaded fuel in 1972.  GM companies tended to cut compression ratios in ’71, while Ford and the Chrysler companies were more conservative in this regard.  Average engine displacements remained high, an indication that automakers weren’t jettisoning their large engines (yet).  Keep in mind that these are simple averages that don’t take into consideration the numbers of engines sold.  There were indeed fewer large engines sold, especially after 1971.

Average Engine Age

The Engine Age graph shows a trend that you might have expected.  The rate that new engines were being introduced and older ones retired declined throughout the era, resulting in the trend of increasing engine ages.  How far back in time do you have to go to find average engine ages higher than the 5.44 years of 1974?  Why, 22 years back to 1952.  The period of 1955 through 1959 saw average engine ages of one year or less!

Gasolene Prices

Average fuel prices might have seemingly increased from $.30 to $.50 during this period, but these increases were largely due to inflation.  The constant-2019-dollar values show constant or declining prices with an upsurge in 1973 and 1974.  Remember the Arab Oil Embargo, gas lines and gas rationing in ’73 and ’74?  Supply went down demand remained constant, and the price increased.

Average Octane Ratings

Gasoline octane values increased sharply in the post-war years.  This was necessary, of course, to enable the drastically higher compression ratios that were in use.  In 1946 the compression ratio average was about 6.7:1, rising a full two points in the next decade.  An average of 8.7:1 might not seem like much, but there were already at least two engines in ’56 that had compression ratios at or above 10:1.  This number (2) would double in ’57 and double again in ’58. 

This trend of increasing octanes and compression ratios went hand-in-hand with increasing displacements, horsepower outputs and the use of 4bbl carburetors.  Yes, the muscle car segment helped drive this, but so did the demands of the average driver and car buyer.  Where a straight-six with a 2bbl carb might have been the normal, bread-and-butter engine in the ‘40’s, the ‘50’s saw this transitioning quickly to ‘non-performance’ V8 engines as the base engine.  In fact, automakers had greatly miscalculated the demand for the new V8 engines.

Chevrolet Engines

Chevy came into 1964 with two small blocks, one of which (283) was long in the tooth, and the other (327) being two years old.  The 409 was the big block offering, with ’64 being its fourth year.  Things were going to change soon, though, with the legendary Mark IV big block making its entrance in 1965.

No other automaker had the one-two punch that Chevy did, of a high-performance small block and a monster big block.  This is in stark contrast to the Chevrolet that entered 1955, with nothing even remotely resembling high-performance. 

There were three V8 engines in 1964, the 283, 327 and 409.  1965 would be the last year for the 409 and the first year for the Mark IV 396.  The very next year, the Mark IV 427 would be added to the lineup.  1967 would see the last use of the 283 and the introduction of the eventual replacement for the 327, the 350cid V8.  These two engines would co-exist for three years, ’67 – ’69.  1967 would also begin the three-year run for the DZ 302, the Z/28 Camaro exclusive engine.  Finally, 1970 would herald the replacement of the 427 for automotive use by the Mark IV 454.  There would also appear the 307cid V8 and the 400cid V8, but these low-performance engines were of little consequence during this era.

The cell hp values indicate Lowest Value / Highest Value.

Chevy ‘Mark I’ 409

The 409 and the 396 existed side-by-side for only one year, 1965.  Remember, the 409, fine as it was (pun intended), was based on the 348, which was introduced in 1958, itself appearing in 1961.  The 409 was a competent engine relative to its contemporaries, with big valves and ports, and plenty of carburetion, but the combustion chamber-in-block was a technological dead end.  Chevy simply wanted a better head, and the Mark IV was the solution.  See 409 in 1946 through 1963 Engine Development by Automaker section of Early US Automotive History.

If the 409 heads weren’t some of the most attractive ever, then I don’t know what. Add chromed valve covers and they were pure art. When looking at the valve layout, it’s easy to see how the valve cover had to be so wide and why it was ‘W’ shaped.

What a gorgeous engine! The huge, chromed valve covers, and the chromed air breather are stunning!

Chevy Mark IV 396

The 396 was the initial member of the Mark IV family but would have the spotlight to itself for only one year, with the 427 arriving in 1966.  The Mark IV design was mostly a “clean sheet” design, with technology adapted from earlier Chevy engines. The top-shelf L78 made over 1hp/in³ in the Corvette (425hp), while likely making more than the rated 375hp when installed in lesser Chevy platforms.

Mark I/II/III?

The natural question is “What’s with the ‘Mark IV’ (4) name?”.  The two generations of Chevy bigblocks were the 348/409 ‘W’ engines and the 396/427/454 engines.  There was no ‘Mark I’ until the Mark II came along in 1963, as a race-only NASCAR engine of 427cid.  Not made in any quantities, there were even smaller quantities of other displacements, such as 396cid.

The Mark II ‘Mystery Motor’ was a race-only, very low production engine that was a combination of the Mark I and design features of what would define the Mark IV. The 409cid version was designated as ‘Mark II’, while 427cid version were known as ‘Mark IIs’. Less than 50 engines were produced.

There was not really a Mark III series, but this designation was given to Chevrolet’s investigation into the potential purchase of Packard’s defunct V8.  The block had huge bore centers and would have been readily made to work up to 500 cubic inches but was overall a conventional and unremarkable design (hey, it was Packard!).  That’s how the series following the 348/409 became referred to as the Mark IV.

The Mark IV engines became known by the slang term ‘rat’, to differentiate them from the already existing smallblock family, which then became referred to by ‘mouse’.  As in “Mighty Mouse”.  Because, well, they were.  Mighty, that is.

Mark I – Mark IV Comparison

Blocks

The mark IV shared the 4.84” bore centers of the Mark I, as well as the 2.498” main journal size and 2.199” connecting rod journal size.  The deck height of the Mark I was 9.6”, while the Mark IV used 9.8” for the ‘short deck’ and 10.2” for the ‘tall deck’.  The tall deck blocks were used for truck engines, with their taller pistons.  The bottom line is that the essential Mark I dimensions were retained for the Mark IV.  With one exception, that is.  The block of the 409 was cut 14° off of the usual 90°, to create the space for the combustion chamber within the block itself.  This was the distinguishing trait of the ‘W head’ engines.

Connecting Rods

One exception to the above is connecting rod length.  The Mark IV rods were 6.135”, or slightly longer than the 409’s 6.00”.

Valves

The valves used in the Mark IV were of two different sizes.  The high-performance versions received 2.19” intake and 1.72” exhaust valves.  Other high-performance heads, particularly those that were aluminum, used larger 1.84” or 1.88” exhaust valves.  The “regular” heads had 2.06” intakes and 1.72” exhaust valves.

The Mark IV valve sizes were comparable to those of the 409, with its 2.07/1.72 valves for “regular” heads and 2.19/1.73 for high-output engines (380hp+).  Valves were tilted from vertical on two axes.

It’s easy to see the 26°/17° tilt of the valves.  This has at times been referred to as a “pent roof” or “semi-hemi” design, both of which are wrong. It’s true the Chrysler corporation had similar heads that they referred to as “polyspheric” (see 1946 through 1963 Engine Development by Automaker section of Early US Automotive History), but that was to establish a marketing tie-in with the hemispheric heads.  Those heads, as these, are canted valve heads.  Nothing more, nothing less.  Don’t misunderstand; these are great heads.  I just don’t want to put a name on them that doesn’t apply.

Valves were actuated by stamped steel rocker arms mounted on studs, the same setup introduced in 1955 by the smallblock (and thanks to Pontiac).  The ratio used on the Mark IV was 1.75:1.

Heads

The heads of the Mark IV were the essence of the differences between the two engines families.  The 348/409 has an unusual combustion-chamber-in-block design, with the resulting ‘flat’ heads.  The valve placement was staggered, in that the intake valve was placed on the intake side of the head and the exhaust valve similarly placed.  The Mark IV retained this design element but went one step further.  The valves were tilted, or canted, toward the intake port and exhaust port, respectively.  The tilt of the intake valves is 26°, with that of the exhaust valves being 17°.

Valve Stems Pointing Everywhere!

If you were used to seeing the valves of an engine with all of the valve stems parallel and in a row, then a Mark IV head was certainly going to look odd, with its valve stems seemingly pointed all various directions.  It’s this nature that earned them the name “porcupine heads”.

Port and Combustion Chamber Shapes

In addition to the several different valve size combinations (2.06/1.72, 2.19/1.72, 2.19/1.84, 2.19/1.88), Mark IV heads were also provided in rectangular port and oval port configurations.  There seems to be some confusion regarding just which engines had which valves, especially on the exhaust side.  The 375hp+ engines received the 2.19” intake valves, but when it comes to the 450/460hp LS6, some sources indicate 1.77” exhaust valves and some sources say 1.88”.

The oval intake ports were smaller than the rectangular and performed better at low engine rpms.  The oval ports were better for street or street/strip applications. Rectangular intake ports were larger than the oval ports, but the big ports made for lower air-fuel mixture velocity at lower engine speeds, which didn’t help low-rpm performance.

Here are the huge rectangular intake ports.

As if that weren’t enough variety, Chevy added to the mixture two different types of combustion chamber designs, open chamber and closed chamber.

For a given compression ratio, consider an open chamber with its domed pistons and a closed chamber, with its relatively flat top pistons.  During combustion there are going to be two very differently shaped combustion chambers for the flame front(s) to traverse.

The open chamber heads were more conventional than the closed chamber.  The closed chamber heads had combustion chambers with more area on the flat portion of the head, which caused the piston to ‘squeeze’ or ‘squish’ the fuel mixture here into the rest of the combustion chamber.  The swirl that resulted helped keep the mixture well mixed.  This also aided the combustion process in that a swirling mixture will help the combustion to distribute throughout the chamber.

At some of the high compression ratios that were used, the open chamber heads required domed pistons.

A 396 is a 396 is a 396, right?

I knew a guy back in the ‘80’s who had a Chevy pickup with a transplanted 396.  To say he was proud of it would be an understatement.  I don’t think he knew much about the engine, really, and he seemed to be under the impression that all 396’s were ‘high performance’, that is, 375 hp or 425 hp.  I don’t think he referred to it as a ‘Vette motor’.  That was a ubiquities term for any Chevy big-block that had been transplanted into another vehicle.  Must have come from a Corvette, right?  And all ‘Vette motors’ were high-performance, too, right?

C’mon, Chevy! 396 or 402?

There doesn’t seem to be any consensus about why Chevy gave the 396 a little 0.031” bore to make into the ‘402’, and then continued to refer to it (mostly) as a ‘396’.  It was in the fifth year for the 396 (’69) that they undertook this little exercise in dumbassery.  People already knew the 396, and making it a ‘402’ didn’t gain anything.  Remember, GM ‘officially’ would not allow an engine bigger than 400cid to be installed in an intermediate or smaller vehicle.  The ‘402’ debacle seemed to fly in the face of this.  None of the handful of different reasons I’ve read make any sense.

New Rochester Quadrajet Carburetor

The Mark IV 396 saw the introduction of the wonderful Rochester Quadrajet 4 Bbl. Carburetor. This was the industry’s first 4 bbl spread-bore carb.

The difference between the Q-jet and other 4 bbl carbs, including those made by Rochester, is the spread-bore characteristic that saw two small primary barrels and two much larger secondary barrels.

The image above shows the two small primaries, with the choke valve open, and the large secondary barrels that are obscured by the closed air valve (bottom). The latter secondaries are characterized as “vacuum”, as the air valve is opened by air pressure (“vacuum”) rather than being linked to the primary butterfly valve.

A bottom view of the Q-jet clearly shows the “spread-bore” design of the primary barrels.

Quadrajets were typically 750 cfm, with some select makes/models receiving 800 cfm units. The choke system had the temperature sensing element mounted in the intake manifold (4MV) or in the carb itself (4MC). The smallish primary bores allowed normal driving airflow to be relatively high, which provided strong vacuum signals to the carb. This higher velocity airflow also importantly provided good mixing of air and fuel, even at lower engine speeds.

The huge secondaries provided the extra air and fuel for full throttle performance. The secondary air valve limited the airflow through these barrels until manifold vacuum (and airflow) forced them open. This, along with the carb’s accelerator pump, prevented the bog that would happen if the secondaries were snapped open when engine speed was low.

The Q-jet was so respected that other automakers, including Ford, purchased it for use on their engines. The Rochester Quadrajet would survive into the 1990’s, after being modified for electronic control.

Other 4-Barrels

Carter manufactured a large number of one, two, and four barrel carburetors that were used for decades by all automakers. Carter was a major player in the OEM market, as well as the aftermarket.

Chevy Mark IV 427

Pretty much everything previously stated about the 396 also applies to the 427, which was a 0.24” stroke increase of the 396.  The 427 had the same 2.50” main journals, 2.20” rod journals, block, heads, valves, etc.  However, there would be some near-full-race versions of the 427, all of them produced in low numbers, that would later be the stuff of dreams.  These engines, going by such RPO codes as L88, L89 and ZL1, would be enormously expensive, but would make way, way over the factory-rated horsepower figures they shared with much more mundane 427 versions.  Yeah, we’re talking 500hp+, pretty much as-is! 

This is the workhorse L36 engine, making 390hp.

Only 435hp…?

You might ask why some of these engines were intentionally under-rated by the factory.  Chevy wasn’t interested in selling significant numbers of the L88/89 or the ZL1 engines.  It didn’t make sense to have hundreds of these race-specific engines on the street, and there was no way they were going to make money on these engines, given the huge prices and limited demand at these prices.  This would still be true, even if they had chosen to advertise the true horsepower.  I have to believe that these engines didn’t even begin to recoup the R&D and tooling costs that went into their production.

I’m not sure what the answer is, but my gut feeling is that Chevrolet let their engineers do something that is rather unlikely these days, that is, to play around and see what they could come up with.  How high could the bar be raised?  In these days of “shareholder equity” (stock price) is everything, we may never see this type of thing again. (Not to mention the feds requiring every engine change to be given their blessing…)  (See Understanding Horsepower and Torque for information on factory ratings).

Chevy Mark IV 454

The gloves came off for GM in 1970.  They dropped their inane self-imposed displacement restriction and went for it.  (If the restriction was so damned important in the first place, why did they decide to compromise it now?)  I’m sure they could see the end of the muscle car movement staring them in the face.  Maybe they just said “Screw it!”  Or maybe one of the top brass grew a pair?  Who knows?

The bottom line is that the ’70 midsized cars could now have engines greater than 400 cubic inches, which meant the 427.  But why stop there?  After all, Buick had their 430, Pontiac their 428 and Olds their 455.  The solution? Stroke the 427 to an even 4.00”, of course!  Four hundred and fifty-four cubic inches.  An inch shy of the Olds, as well as the 455s that Buick and Pontiac would field, but who cares?  The hottest 454 versions would eat the BOP 455s for lunch. (I wouldn’t make this statement in reference to the Buick 455 Stage 1, though!)

The top of the 454 heap would be the famed and feared LS6, making 450hp.  This was more than the factory rating of any other engine.  Sure, the 426 Hemi would have come in at about 475hp if Plymouth and Dodge hadn’t fudged the numbers, but c’mon!  This was a freakin’ monster, with all of the right ‘go-fast’ parts:  big ports and valves (iron head), high-rise aluminum intake, 850 cfm Holley carb, solid lifter cam, forged internals, high compression ratio, etc., etc.

There were to be no ‘limited production, race-specific’ versions of the 454, but that’s okay, and it’s perfectly understandable.  There just would be no reason to go this route, having explored it with the 427.

COPO? Is that a Disease or Something?

Chevrolet had a system referred to as Central Office Production Order (COPO) that seemed to exist to circumvent the GM self-imposed horsepower and displacement regulations.  While you couldn’t ‘officially’ buy your ’69 Camaro with anything hotter than the 375 hp 396 (pretty damn hot as it was!), the right COPO option could get you the same car, but with a 425 hp 427 under the hood!

It was kind of a cool thing, allowing someone to have a vehicle that the vast majority of purchasers didn’t even know about.  A measure of exclusivity.  But really, Chevy?  Just pick a way and go with it and dispense with the ‘under the table’ BS!

Chevrolet Small Block V8 Engines

283cid V8

The second iteration of the small block, the 283, was offered well into the muscle car era as Chevy’s base V8.  You’ll recall that this was the second small block, after the 265, and appeared in 1957.  In its ’64 to ’67 existence, it was a mere shadow of the 283/290hp days.  Still, it was a good little engine and entirely suited to low-compression (9.25:1), two- and four-barrel, base engine duty.  It was rated at 195hp with a 2bbl carb and 220hp with a 4bbl.  (See 1946 through 1963 Engine Development by Automaker section of Early US Automotive History for ’57 – ’63 283 info.)

Introduced in 1957, the sweet little 283 was still around through 1967. Like the ‘ram’s horn’ exhaust manifolds?

302cid V8 (DZ 302)

This little gem was introduced in 1967 as the engine for the Camaro Z/28.  It would serve in that capacity for three years, through 1969.  Unlike the Ford 302, there were no lower-production versions of this engine.  It was 290 hp or nuthin!

The ‘DZ’ 302 was borne of the desire by Chevrolet to race in the Sport Car Club of America (SCCA) Trans Am racing series.  It limited engine displacement to 5 liters (litres, for you European types), or about 306cid.  To get such a displacement, Chevy took the 327 block and heads and installed the crank from the 283.  This made for the desirable ‘big bore’ and ‘short stroke’ of 4.00” x 3.00”.  This would incidentally be the same bore/stroke of the Ford 302, introduced in 1968.

Not surprisingly, this engine was designed for high-rpm power, possessing a redline of some 7,000 rpm.  Heads were from the fuel-injected 327, with 2.02” intake valves and 1.60” exhaust.  Internals were forged, and the pistons made for an 11.0:1 compression ratio.  Induction was provided by a 780/800 cfm Holley carburetor sitting atop a dual-plane, aluminum high-rise intake manifold.  The camshaft was an aggressive “Duntov 30/30”, with solid lifters.   Specifications for the cam are .452″ intake and .455″ exhaust lift, 229° intake duration and 237° exhaust duration (both measured at .050″ tappet lift) and 78° of overlap (at 0 lift).

Only 290hp?

The DZ was factory rated at 290hp @ 5,800 rpm and 290 lb.-ft of torque at 4,200 rpm.  It’s been long rumored that the engine power was substantially under-rated by Chevrolet.  Figures have been published, based on “guesstimation” or mysterious, midnight dyno runs, that range from 350hp to “well over 400hp”.

The DZ 302, like the Ford Boss 302 that arrived in 1969, was indeed under-rated by the factory. The best evidence supports this as being true, although the extent of the under-rating is a little harder to pin down. It’s likely this was a 340 – 350hp engine in factory trim.  (See Understanding Horsepower and Torque )

The Z/28 was capable of very low 14 second quarter mile times.  The gearing was appropriate for a smaller, high-revving engine, being in the range of 3.73:1 to 4.11:1.  A well running Z/28 could walk all over an unsuspecting big block car, especially one that had more “daily driver friendly” rear-end gearing.

307cid V8

This engine merits only a quick mention.  It was the replacement for the 283 as the base V8, and it never enjoyed a period of time where it was a performance engine.  It was strictly an economy V8.  All versions breathed through a 2bbl Rochester carburetor, and the initial ’68 engine was rated at 200hp.  By the time 1974 came around, the SAE net rating was a big 115hp.  Compression ratios started at 9.0:1 and ended up at 8.5:1.  Valves were 1.725″ (I) and 1.515″ (E). Can you say “Meh”?

327cid V8

The 327 was the Chevy smallblock workhorse of the 1960’s that the 350 would become regarded to be in the 1970’s and beyond.  This engine, of course, was the result of a bore and stroke of the 283, to 4.00” by 3.25”, and appeared in 1962.

Although offered in versions with outputs as low as 210hp, the 327 would never be relegated to ‘also-ran’ status, like many engines were.  In 1967, its next-to-final year, there was still offered a 350hp version, reaching the magic “one horsepower per cubic inch” barrier.  (See 1946 through 1963 Engine Development by Automaker section of Early US Automotive History for ’62 – ’63 327 info.)

I’ve always thought that the Chevy small block really came into its own with the 327. Even in the 2020’s people are still putting 327’s into project cars. Not so much for the 265 and 283.

350cid V8

Cars were getting heavier, and it was felt that the 327 could use a boost in displacement.  This it got in the form of a 0.125” stroke, becoming the much acclaimed 350 in 1967, with its 4.00″/3.48″ bore/stroke.  For the first two years, it would be a 295hp optional engine for Camaro and Chevy II.  Keep in mind that for ’67 and ’68 the 327 was still offered in a 350hp flavor.  1969 was the transition year, with the 350 stepping up to 350/370hp and the 327 doing low-compression duty in 210 and 235hp versions. Most 350’s had valves of 1.94″/1.50″, with the highest outputs being 2.02″/1.60″.

Nobody else offered the number of high-performance small blocks that Chevy did, with their 300hp+ 327s and 350s.

1970 350 LT-1

The high-water mark for the 350 was the 1970 LT-1.  This engine is talked about in hushed tones; it has the air of something spiritual.  It contained all of the right goodies: fuelie heads with big valves, 780cfm Holley mounted on a high-rise aluminum intake manifold, 11.0:1 compression ratio, and a hot solid-lifter camshaft.  The result was 370hp at 5,800 rpm in the Corvette and 360hp at 6,000 rpm in the Camaro.  We’re talking about 1.057hp/cubic in.

This combination was capable of big block horsepower figures and had a lot less weight over the front wheels.  You could have yourself a sweet handling Corvette or Camaro with this setup, one that didn’t have to shy away from a straight-line contest, either.

Wanna know how many ‘hot big blocks’ were humiliated by arrogantly challenging an LT-1?  A lot, that’s how many!

400cid V8

The 400 was the largest of the Chevrolet small blocks and was in no way a high-performance engine.  As with the low-po 307, we’ll just cover the essentials.

The Chevy 400 was the largest small block made, with its 4.125 in. bore.  The result of this was that there wasn’t enough space for coolant passages between the bore pairs.  These ‘Siamesed’ bores were without a doubt a compromise design.  The connecting rods weren’t as beefy as those of the 350, again due to space limitations.  The 4-bolt blocks were dropped in favor of 2-bolt.  One has to wonder why they went to the trouble of 4-bolt mains in the first place.  It graced us with its presence in 1971. The engine lived through ’76 in Chevy cars and ’80 in trucks.  One thing it did accomplish was to put Chevy in the odd position of having a small block engine that had greater displacement than their smallest big block!

Buick Engines

The Buick story is about the 455, when it really comes down to it.  Yeah, there was the 425, which was then bumped up a whole five cubic inches to become the 430, and then another generous twenty-five inches to the famous 455.

But what about the 401, and later the 400?  These were some pretty okay engines, right?  Well, yes and no.  The 401 Nailhead wasn’t a bad engine, it just wasn’t a great engine.  By 1966, the last year for the 401, it was in its eighth year.  The engine was designed with small valves and ports, and with a pent roof kind of combustion chamber that required the valves to be aligned vertically, not in line with the cylinders.

At a time that a Pontiac 389 offered up to 360hp, the Buick 401 was limited to 325.  Not bad, but not really competitive.  When the new 400 replaced the 401 in 1967, the power was bumped up 15 to 340hp.

A GS 400 could be nicely optioned and would make for one of the ‘nicest’ performance cars to be had.  Nice looking exterior, nice wheels, nice seats, dash, etc.  But there were few if any performance options that would allow a buyer to create something really ‘go fast’ oriented.  It could be nice, responsive, even quick, car.  Never going to be a boulevard bruiser, though.

It’s kind of interesting to note, when looking at this chart, that the 455 made only 10hp more than the 425, which was introduced in 1963.  In fairness, though, the 425 used a 3 x 2bbl setup to get its 360hp, while the 455 had a single Quadrajet carb.

Buick Small Block V8 Engines

300cid V8

It’s been said that the Buick 300cid V8 was based on the 225cid V6. The engine served as the base V8 for a number of Buick models and was available in a 250hp version for ’64, its introduction year, and for ’65.  The 300 shared the bore spacing (4.24”) of the 225 V6, as well as the bore and stroke of 3.75” x 3.40”.  Bearing sizes were 3.00” for the mains and 2.00” for the rods. The 340 and 350 shared the same bearing sizes.

Valves were a smallish 1.625”/1.313”.  In ’66 these were bumped up to 1.8175”/1.38”.  Buick small blocks had deck heights of 10.187” and a connecting rod length of 6.385”.

The 300 didn’t play a big part in Buick’s legacy, performance or otherwise.

The 300 replaced the all-aluminum 215 and was a less expensive alternative. Unfortunately, it was a technological step backward.

340cid V8

In its third year, 1966, the 300 was stroked 0.450” to produce the 340cid V8.  The 300 would stay around through 1967, overlapping with the 340 for two years.  With Buick models getting larger, like all others, it was thought that 300 cubic inches was a bit small.  The 340 bore and stroke were 3.750” x 3.850”.  It had the same valve size as the later 300 V8s, at 1.8175”/1.38”.

350cid V8

The 340 itself was only available in 1966 and 1967 before it received a 0.050” bore, resulting in the 350cid V8.  With a bore and stroke of 3.800” x 3.850”, the engine was almost exactly square.  The 1970 version of the GS 350 made 315hp, by far the highest specific output of the Buick small blocks.  All three engines shared 3.00” main journals and 2.00” rod journals (rounded).  The 350’s valves were 1.88”/1.50”.

The Nailhead Engines

401cid V8

The 401 Nailhead was in its sixth year in 1964 and would soldier on through 1966.  Its tiny valves and odd head design limited its opportunities for further development, not to mention its significantly over square design.  A new design was needed, one with more conventional heads and more competitive valve sizes.  This would be the 400cid V8.  401 vitals: bore/stroke – 4.1875” x 3.64”; valves – 1.875”/1.50”; bearings – 2.5” main, 2.25” rod; deck height – 10.025”.

The 401 Nailhead is covered more completely in 1946 through 1963 Engine Development by Automaker section of Early US Automotive History.

425cid V8

The 425 was basically a bored 401.  It shared the 401’s small valves (1.875”/1.50”), odd heads and small 2.5” main journal size.  The 360hp versions had dual Carter carburetion, but all 425s were relegated to ‘large cars’, with their bloated weights and lazy rear-end gearing.  Responsive cars, for sure, but hardly ‘fast’.

Still a Nailhead…

The 425 heads were different, as this engine was a Nailhead.  As such, it had the Nailhead odd-shaped combustion chamber, sometimes referred to as ‘semi-pent-roof’.  All of the major dimensions were shared between the 401 and the 425, except for the cylinder bores, which was 4.3125” for the 425.

Notice how deep the top part of the combustion chamber is in the image above.

The Buick 425 piston looks more like a 1954 piston than a 1964 piston, doesn’t it? No ‘slipper’ designs here folks! Buick just reshaped the crankshaft counterweights to allow the pistons to clear.

Here’s a Chevy 427 piston, which is a slipper type, to compare with the Buick. And, no, the Chevy isn’t that much larger than the Buick; it’s just the image size!

The 425 and 430 engines were strictly for the larger Buicks, and while some versions were certainly ‘sporty’ and ‘responsive’ Buick didn’t have any take-no-prisoners’ versions of their big block like Chevy did, with their 409hp and 425hp 409 V8s.

One thing that was a bit odd about Buick and their engine references was their use of torque figures in naming their engines.  For example, they had the Wildcat 310, 350 and 375.  In displacement, these were 300, 340 and 340cid, respectively.

Should We Just Eliminate all Ratings?

The first time I saw a Buick engine with its designation on the air breather sticker, it confused me. Torque? Reminds me of looking at lawn mowers at my nearest super-center last season. No Briggs & Stratton horsepower ratings as in the past. Now we have something called ‘peak torque’! Exactly what the heck is that?

I also made the mistake of looking at A/V receivers at a different store. I’m in electronics and have been interested in audio high fidelity for ages. Not super-exclusive, high-priced stuff though. Anyway, they had some units that were fairly inexpensive and that were rated at between 300 and 500 watts. Plus, they were powered off of a 12V wall-wart! What happened to the ratings that were so carefully put in place in the 1970’s? Seems that amplifier output power today is pretty much arbitrary.

I think I’ll just put some music on and forget this whole mess. My system is rated at 1.21 Gigawatts, don’t you know!

400cid V8

The 400 gave Buick a conventional V8 that was at the self-imposed 400cid GM limit for mid-size and smaller cars.  The engine was used primarily as the powerplant for the GS 400.  It was a solid engine, but really not remarkable in any way.  There were no high-performance versions of this engine, which would only last until the 455 appeared in 1970.  That’s when things really got interesting.

The 401’s 1.15 bore/stroke ratio was out of step with contemporary design practices.  Over-square was the geometry of choice, just not this over-square!  Their 400 had a much more common ratio, being slightly over-square.

The Buick 400 combustion chambers were fairly conventional, being wedge-shaped and having a squish/quench area.  Intake valves were 2.00” and exhaust 1.625”.  Not exactly huge, but waaay bigger than the Nailhead.  Where the 401 had small, 2.50” mains, the 400’s were 3.25”.

The 400 retained the 4.75” bore spacing of the Nailheads, and in addition to the larger main journals, the main caps were also beefier.  As with the previous engines, all blocks used two-bolt mains.  Connecting rod length was 6.607”, with deck height being 10.57”.

430cid V8

The 430 was the larger ‘sister’ to the 400, both having arrived in 1967.  The engines shared the same basic dimensions, with the 430 having the same stroke and a larger bore.  Bore/stroke: 4.1875” x 3.90”.

Like the 425, it was solely a ‘large car’ engine.

It’s interesting to note that the 430 made the same 360 hp with a 4bbl carb that the 425 did with dual 4bbl carbs.  The 430 bore/stroke ratio, at 1.074, was much less over-square than the 425 was.

Buick 455cid V8

The Stage is Set!

It’s said that there are times, rather rare times, when a machine comes together to become far more than the sum of its parts.  Could be an engine, an aircraft, a car, a tractor, or any of a number of different machines.  While there are other examples one could cite, I know that this definitely applies to the Buick 455, particularly the Stage 1 version of the engine.

The 455 was one of the first “thin-wall casting” engine blocks at GM, and because of this advance in production technology, it weighs significantly less than other engines of comparable size.  For example, it weighs 150 lb. less than a Chevrolet 454 and only 25 lb. more than a Chevrolet 350.

A GS 455 was not a particularly light car, with an automatic car with fuel and oil pushing 4,000 lb.  The steepest gear readily available were 3.64:1, so no killer 4.10s or 4.33s for this car.  Still, a well-running Stage 1 car would be good for mid-thirteens and would be a threat to any 426 Hemi, Super Cobra Jet 428 or LS6.

A 455 is a 455, Right?

What made this engine so special, so much different from an Olds or Pontiac 455?  At first look, very little.  But its output was something else altogether.  It combined incredible low rpm torque, a broad, powerful midrange, and a respectable 360hp peak.

There are numerous articles that have been written over the years that would cast doubt on the factory 370hp rating of the Stage 1.  Statements made by former Buick engineers would indicate that the power ratings of the three versions of the 1970 455 were conveniently placed at 350, 360 and 370hp.  Given the trap speeds of some stock Stage 1 cars, performance calculators would indicate an actual output of some 400+ hp.

On paper, a 455 Pontiac or 455 W30 Oldsmobile would seem to perform similarly to a Stage 1, but that simply has not been the case.  For an engine that seems to make some 30 to 50hp more than its rated figure, the Stage 1 possesses a staggering amount of torque at a ridiculously low rpm.  This combination seems to be magic, like there’s something else that’s there, but you can’t seem to account for it.  More than the sum of its parts?  Yeah, I’d say that about the Stage 1, no question.

Bore/stroke: 4.3125” x 3.90”.  Valves were 2.00”/1.625” for most, with the Stage 1 sizes being 2.12”/1.75”.

This special air breather was designed to seal to the underside of the hood for the functional hood scoops.  With it, the 455 Stage 1 looked intimidating.

Stage II

The mere thought of the Stage 2 option makes a Buick guy’s heart race.  This was maybe the least ‘Buick’ kind of option you could think of.  This was a dealer-installed option that included Stage 2 heads, cam, high-compression pistons (12.0:1), Edelbrock manifold, Holley carb, Mickey Thompson headers, and (wait for it…) 4.78:1 gearing.  Holy Crap, Martha!

Oldsmobile Engines

1964 saw Olds with two V8 engines, their small 330 and the 394.  This would be the last year where these were the sole V8 offerings.

The next year, ’65, would see the introduction of the sister engines, the 400cid V8 and the larger-car V8, the 425.  The 425 was a 1/8” bore of the 400.  The 425 would be replaced by the 455 in 1968, which shared the 425’s bore, but with a 0.270” longer stroke.  This would give the Olds 455 under-square dimensions, which had been abandoned by most automakers.

Under-Square…?

Few, if any, engine families were being designed at this time with under-square dimensions.  I doubt Olds specifically wanted an under-square 455.  It seems reasonable that the 425 block limited the bore to 4.125”, at least for efficient manufacturing.  How to get the additional 30 cubic inches?  Have to look to increasing the stroke.  These engines did make gobs of torque, no question.

It’s kind of interesting to note that the highest output 455 (400hp) made 0.8791 hp/cu. in., which is lower than the highest output 350, 400 or 425!  To equal the specific output of the 325 hp 350cid V8, the 455 output would have to be 422hp!  The highest rpm value listed for horsepower specs of the 455 was 5,000 rpm.  Olds wasn’t generally interested in high engine speeds to begin with, and it’s certainly true of their 455.

To be fair, the Olds 455 wasn’t the only under-square 455, as Pontiac’s was, too.  The Pontiac 455 was just slightly less so than the Olds engine.  Buick’s 455, on the other hand, was a thoroughly modern ‘slightly over-square’ design, yet it made as much torque as either of the other two.  Go figure.

The little 330 was available in versions making well over 300 hp, and it was in essence a little screamer.  It just wasn’t going to have the cubes it needed going forward.  It was a modern engine design, and a simple bore increase resulted in the 350 that would serve Olds well into the ‘70’s.  The 394 was certainly respectable, but it wasn’t the design that was going to take Olds into the last half of the ‘60’s, and into the ‘70’s.  Remember, this guy was introduced in 1959!

Do ‘Small Block’ and ‘Big Block’ Apply to Olds?

Most assuredly, yes, they do!  The 330 and 350 had a deck height of 9.330 in., while the Big block 400, 425 and 455 had deck heights of 10.625 in.  The delineation point in time for the Olds evolution to two different block sizes is the year 1964.

Olds 394cid V8

1964 was the final year for the 394, which was by then in its sixth season.  The new 400 would replace it in ’65, and there would be no overlap between the two engines.   Given the closeness in displacement, this makes perfect sense.  Notably, the 394 would never be de-tuned and relegated to base V8 duty.  See 1946 through 1963 Engine Development by Automaker section of Early US Automotive History for more information on the 394.

I suspect that if you were to say “Olds 394” to anyone but an Oldsmobile fan, you might get blank stares.

Olds 330cid V8

The 330 arrived in 1964 and was the first Oldsmobile small block V8. It’s deck height was 9.330″, with a bore of 3.398″ and stroke of 3.385″. Crank journals were 2.495″ and rods were 2.00″. Valves were smallish at 1.875″ (Int) and 1.562″ (Exh).

425cid V8

This engine replaced the 394 in 1965. Bore and stroke were 4.125″ and 3.975″, respectively. Valves were larger than the 394cid predecessor, at 2.07″ (Int) and 2.00″ (Exh). Deck height was 10.625″, making this a big-block engine.

The 425 was the sister to the 400, both engines being introduced in 1965, and sharing strokes of 3.975”, as well as deck height, bore centers, bearing sizes, etc.  Its bore value was set at 4.125”.  The 425 would make up to 385hp in the top Olds luxury/performance model, the Toronado.

The top 400 and 425 versions would have specific outputs just over 0.9 hp/in³.  Which normally aspirated Olds engine had the highest specific output?  The 315hp version of the little 330, at 0.954 hp/in3!

A Vintage Source Highlights the New Olds 330 and 425

Car Life, October 1964, (see Sources) had a great article about the ‘new’ 330 and the upcoming 425.  The following couple of paragraphs summarize the gist of the article.  It introduces the new for ’64 330 and the 425, released in ’64 for the ’65 model year.

The original Rocket engine of 1949 was the 303cid V8.  It Had a bore/stroke of 3.75” x 3.437”.  In 1954 the bore was increased by 0.125” to make the 324.  The 371cid V8 arrived in 1957, thanks to a 0.125” bore and a 0.250” stroke.  The engine retained the original 1949 4.625” bore centers.  In 1959, an additional 0.125” bore brought us the 394cid V8.

Oldsmobile engineers were concerned that they might be impacting engine reliability and longevity by pushing the original design parameters too far.  This led to them to increase the block deck height, the connecting rod length and the main and rod journal sizes.  Crank pin overlap was also increased during this process.  Finally, the intake valve size was increased from 1.75” to 1.88”. (Emphasis mine)

Dynamite in a Small Package

Olds wanted a suitable small engine to replace the aluminum 215, which was based on a Buick design.  Both Olds and Buick were rethinking the all-aluminum idea.  They investigated what it would take to make their existing V8 work, in a smaller displacement.  Their solution needed to be cost effective, which ideally meant a design that utilized the already-existing production machinery.  This would mean keeping the existing bore center dimension, lifter bore dimensions, and camshaft-to-crank dimension.

What to do?  Recast the block and heads, making them smaller and lighter, while retaining the key dimensions.  Using state-of-the-art casting techniques, they reduced block wall thickness from 0.22” to 0.18”, by controlling the degree of core shifting.  This was an example of thin-wall casting.  It was decided to change the valve angle from 17° to 6° and to place the valves in the center of the combustion chamber.  This paid off in a head that wasn’t as broad, as well as lighter weight.  The new small block fit the F85 engine compartment and accomplished everything the Olds engineers desired.

The article pointed out that the initial 425 blocks would not be thin wall castings, due to foundry capacity issues.  The October 1964 issue of Popular Science stated that the 425 block and heads were thin wall castings.

The 330 and the 425 actually shared several components, which was unusual.  The 425 ports were roughly 25% larger than those of the 330.  It also additionally had a hotter camshaft.  425 rocker arms were interesting in that they were of the same general post-mounted type of their GM sisters, but the Olds rockers would only pivot along one axis.  Olds engineers felt that this added stability and was in general a better design.  The 330 would later be modified to utilize this design.

Olds 400cid V8

The new Olds big block engines appeared in 1965, consisting of the 400 and the 425.  The deck height was 10.625”, versus the earlier 9.330”.  Main and rod journals remained 3.00” and 2.50”, respectively.

The heads featured larger ports and valves than the 394.  Intake valves measured 2.00” and exhaust 1.625”.  For the high-performance engines, intake valves measured 2.072”.  All blocks use two-bolt main caps.  The 400 was less over-square than its 394 predecessors, in keeping with industry trends.

The high-water mark for the 400 was the ’66 version, making 360hp with 3 x 2bbl induction.  The 400 was not substantially larger than the 394, obviously, but it was a more modern design.  It’s a bit interesting that, with larger ports and valves, the highest performance 4bbl 400 made the same rated horsepower and torque as the top 4bbl 394 did.

W-30 Goodies

Olds did have a sweet setup for the optional, high-output engines, at least in some models.  Look at the cold air intake hardware on this Ram Rod 400!  This was a big part of the ‘W-30’ option, the package that gave you the highest output 400, as well as some other goodies.  The air came from the intakes mounted below the front bumper, not through the hood.  The battery was in the way, so it was relocated to the trunk for cars with this option.  (See I Love Hood Scoops for an idea of how well this cold air setup might have worked.)

The heads Oldsmobile used were fairly well designed.  Nothing too crazy, just a good, solid design.  They had conventional wedge-shaped combustion chambers of the ‘open chamber’ design, with a squish/quench area.

Olds was known for many good things.  Their intake and exhaust manifolds were not among them.  This is representative of a high-performance exhaust manifold.  Compare to a Pontiac set to get a perspective.

Intake manifolds were typically of the low-rise type, forcing the incoming air/fuel mixture to make rather sharp turns.

It’s hard to get the true feel of this manifold from this small picture. If you ever get the chance to view an Olds intake and a Chevy or Pontiac side-by-side, you will be able to appreciate the differences.

Here’s another image of an Olds 455 intake manifold from one of their higher rated engines. Hopefully this different angle will better illustrate that these manifolds possessed no “high rise” properties whatsoever. Oldsmobile just didn’t seem to worry too much about their manifolds!

Super-Size Me!

The 425 was the top dog at Oldsmobile for three years, ’65 – ’67, when an additional quarter inch was added to its stroke to yield the 455.  Olds therefore beat both Pontiac and Buick to market with the 455.  Collectively, the BOP (Buick, Olds, Pontiac) 455 V8s had some interesting differences, but far more commonalities.  None had compression ratios that were terribly high, two of the three were under-square, valve sizes were generous, but not huge, all typically used cast iron intake manifolds and Rochester Quadrajet carburetors, and all three used iron exhaust manifolds that were generally of fairly common design.  All used heads with common wedge-shaped combustion chambers, small valve angles, and aligned valves.  This was markedly different from the almost-same-sized Chevy 454.

Olds 455cid V8

As previously stated, Olds beat both Pontiac and Buick to the punch in the 455 cubic inch contest, coming to market with theirs in 1968.  This obsoleted the 425.  The 3.975” stroke of the 425 was increased to 4.25”.  The bore remained at 4.125”.

All of the engine blocks Olds used in their big block engines had two-bolt mains.  Crankshafts were either cast iron or nodular iron, while rods were forged, and pistons were cast.  As with the 400 and the 425, valves measured 2.00” intake and 1.625” exhaust.  All three of these engines used larger, 2.072” intake valves on their high-performance heads.  Of course, the 400, 425 and 455, all being Olds bigblocks, shared the 3.00” main journal size and the 2.50” connecting rod journal size. The high-performance 455, named W-30, also featured an aluminum intake manifold, with all of the others being cast iron.

This 455 is fitted with an air breather that seals to the underside of the hood, for the functional hood scoops. Cool.

What’s ‘Nodular’?

Nodular iron, like all iron, has graphite added to it.  In ‘plain old’ iron the graphite exists as very small flakes within the iron matrix.  This contributes to the brittle nature of cast iron, which is not important for many applications.  However, a substance can be added during the forming process to form the graphite to nolularize, or to form tiny nodules or spheres.  This greatly increases the tensile strength of the product and decreases its brittleness.  Why isn’t this done for all iron products?  Simple—it’s often not needed, and it adds expense.

You may have noticed that the hot W-30 455 in 4-4-2 actually made a rated 30hp less than the 455 installed in Toronado! Buick and Pontiac did something similar, but the 30hp gap here is the largest of the group. So, why didn’t Olds install the 400hp job in 4-4-2 as an option? This question is looked at in-depth in Horsepower and Torque. We’ll summarize here by saying that it’s apparent that Oldsmobile under-rated its hottest 455’s and over-rated their big car 455’s. Why they did so is a matter of conjecture.

Olds 350cid V8

The 350, introduced in 1968, was derived from the 330cid V8.  The bore of the 350, at 4.057”, was 0.119” larger than the 330.  It shared the 3.385” stroke of the 330.  The mains, at 2.5”, were the same size, and the 2.125” rod bearings were larger than the 2.00” of the 330.  The 350 also shared the valves of the 330, sized at 1.875” intake, and 1.562” exhaust.

W-31 350cid V8

This little gem was a ’70 and ’71 option.  The engine featured heads with larger valves (1.995”/1.625”), and a slightly higher compression ratio.  The cam was also more aggressive than with Olds’ other 350s.  It’s kinda odd that this 350 made only 5hp more (325hp) than the hottest version of the 330.  This was a nice little engine.  Nowhere near the 370hp of the Chevy LT-1 of the same era, but very respectable nonetheless.

Pontiac Engines

1964 saw Pontiac with four V8 engines, from 215cid to 421cid.  Their 326 and 350 would never be really consequential engines, and the 389/400/421/428/455 mainstays were derived from the 347cid V8 of 1957.

Pontiac heads prior to 1968 used closed chambers, while ’68 and later used open chambers.  Pontiac used machined chambers, rather than as-cast.  The majority of Pontiac pistons were cast, flat-top, and had valve reliefs.

What Do You Mean “It’s Not a Big Block”?

Pontiac was a bit unusual in that they didn’t have ‘small block’ family and ‘big block’ families of engines.  The reason for this was simple – their blocks didn’t vary in external dimensions!

What they did have, though, is ‘small journal’ and ‘large journal’ families of engines!  Anything 400cid or smaller had 3.00” main journals.  The 421, 428 and 455 had 3.250” main journals.  Pontiac blocks had a deck height of 10.24” and bore centers of 4.620”.

Pontiac 326cid V8

The 326 had been introduced the previous year, albeit with a slightly larger bore.  This year the bore was reduced to the 3.72 in. it would have for the remainder of its existence.  The engine came in a 250hp, 2bbl, low-compression version and a 280/285, 4bbl, high-compression version.  Although the engine, as the ‘326 HO’ served as a junior performance engine for the Firebird, it was never truly regarded as a performance engine, having not possessed any high-performance hardware.

Pontiac 350cid V8

The 326 received an increased bore in 1968, to become the 350.  Of course, it was one of four GM 350cid engines, having nothing in common with the 350’s from Olds, Buick, or Chevy.  The ’68 and ’69 HO version would make a very respectable 320hp, but in general, this wasn’t a performance engine.  

Pontiac 389cid V8

The 389 was Pontiac’s key engine from 1959 through 1966.  I believe it will always be regarded as the quintessential Pontiac engine, for all time.  It was this engine, then in its sixth year, that powered the first three GTO iterations.  The Tri-Power option, not new in ’64 but still sexy as all get out, was within reach of the car-buying masses.  Suddenly you could have the performance, if not the room, of a larger Pontiac costing 15-25% more.

The 389 Super Duty models were noteworthy.  These engines featured larger valves.  In addition, SD engines had four-bolt mains, forged crank, forged connecting rods, and forged pistons.  Pontiac took the ‘build it your way’ crown in the huge variety of engines available, all displacing the same 389cid!

Hey, isn’t ‘Super Duty’ a Ford Term?

Well, yes, it is, but Ford started using the term long after Pontiac had quit using it.  It is a rather appropriate term, as used by Pontiac, in that the SD engines were indeed more robust than the general, ‘regular duty’ engines.  I’m sure Ford uses it for the same reason.

In 1959 and 1960, when regular 389s had valves of 1.88”/1.60”, SD valve sizes were 1.92”/1.66”.  The next two years, ’61 and ’62, the SD valve sizes were 2.02”/1.76”.  389 SD engines used a 4bbl carb for NASCAR use and 3 x 2bbl for NHRA.

You know, a 389 Tri-Power was an attractive engine. Maybe not as sexy as a 409 or a 426 Hemi, but still…

Pontiac 421cid V8

This engine was introduced in 1961 and was a tiny bore and 0.25” stroke of the 389, which was in its third year at that time.  The ’61 – ’63 Super Duty versions were legendary for their high output and ruggedness.  The 390/405/410 hp killers were discarded after 1963.  The 421 was the first of the so-called ‘large journal’ Pontiac engines, with its 3.25” main journal size.  This would be significant as the engine size continued to be increased.  See 1946 through 1963 Engine Development by Automaker section of Early US Automotive History for more information about the 421.  Carburetion was from a Carter 4bbl or three Rochester 2bbls.

421 ‘Super Duty’ Engines

This engine was offered for the years ‘61 – ’63, thus overlapping with the 389 SD for two model years.  Unlike the 389 SD engines, the 421 SDs often had compression ratios substantially higher than the production counterparts, as high as 13.0:1.  The carburetors on the 421 SD were either 4bbl, or dual 4bbl.  No Tri-Power setups were used.  The 421 Super Duty engines received the same high-strength items that the 389 SD engines did.  Pontiacs with these engines were, for all practical purposes, race-only.  I’m sure a few did occasionally see some street duty, though.

Take a look at these sculpted beauties!  No ordinary manifolds for the Super Duty.  For weight savings, some were made of aluminum, which, it was said, might shed a drop or two of melted metal after a hard run.  I can’t vouch for the accuracy of this statement; makes a good story anyway.

421 HO Engines

The top 421 V8s for ’64 – ’66 were the ‘HO’ versions.  The majority of these engines were fed by Tri-Power induction.  It’s been said that after the ’63 GM ban on racing activities, there was a shift away from forged internals and four-bolt mains, at least at Pontiac.

Pontiac 428cid V8

The 421 received an ever-so-tiny bore increase in 1967, to become the 428.  Frankly, I’d be interested to know how adding less than 0.03” to the bore, and 7 cu. in. to the displacement, was worthwhile.  The 428 possessed larger valves, and its 390hp version cracked the 0.9hp/in³ barrier, where none of the 421 variants did.  As with the 421, this was strictly a large-car engine.

Heck this could be a 400 for all I know. Pontiac large-journal engines were indistinguishable from one another, especially when the owner was trying to pass off a larger engine as a smaller.

Pontiac 400cid V8

In 1967 the 400 took over from the 389 as the workhorse of the Pontiac lineup.  The heads featured larger ports and valves than the 389 had.  Intake valves were a large 2.11”, with the exhaust being 1.77”.  The head configuration was similar to the other Pontiac V8s.  As with their 389, Pontiac felt compelled to offer a butt-load of different flavors of the 400, from 255hp to 370hp.  Guess that was a Pontiac thing?

Ram Air for the Masses

When Pontiac introduced their 400 in 1967, they also made available the first of a series of optional engines with high-performance heads.  Unlike some of the other automakers, these did not feature different chamber (open/closed) designs, substantially higher compression ratios, or larger valves.  What they did have, though, was somewhat larger intake ports and totally different exhaust ports.  The exhaust ports were, in fact, round.  They greatly outflowed the regular, rectangular ports.

In addition to having larger valves than the slightly smaller 389, the 400 also had a reduced valve angle.  It was now set at 14°, where previously it was 17°.  1967 would also be the last year for closed-chamber combustion chambers.  It’s been said that one of the things motivating the change to open chambers was the emissions regulations that were gathering like dark clouds on the horizon.

The 360 hp 400 of 1967 would later become referred to as the ‘Ram Air I’, though this term was not used at the time.  These heads were closed chamber, with a 14° valve angle.  In addition to an aggressive cam, the engine also featured the beautiful, free-flowing iron exhaust manifolds that the Pontiac performance engines would become known for.

‘Computer Designed’?

This term was at one time kind of a ‘badge of pride’.  Maybe a bit like ‘Solid State’ was.  It’s meaning back in the 1960’s is quite different than it is today.  Maybe that’s not surprising, given that your nothing-special cell phone has more processing power and more data storage than a full-to-the-walls, 10,000 square foot data center did in the late ‘60’s.  You have to remember that a typical mechanical engineer in the ‘60’s had limited access to a computer, of which there was likely only one, a mainframe.  Most of his work was done with a slide rule, since handheld calculators were still a few years away.

Hewlett-Packard’s first scientific handheld was $395, equivalent to nearly $2,500 today!  And this was ’72.

Here’s a K&E slide rule and its case. K&E made some of the better instruments of this type.

the HP-35 was a slide rule that could fit in your pocket. Of course, it was much faster and more accurate than the slide rule. This was a revolutionary electronic product.

Ram Air II

This was the first of the Pontiac round-port (exh.) heads.  This was only in the 1968 GTO. The cam was really aggressive and would live to see duty on the ’69 –’70 Ram Air IV engines.  It’s long been said that the ‘041’ cam was the first in the industry to be ‘computer-designed’.  The 366hp rating was well short of the real value. This 1968 engine would reappear in 1969 as the Ram Air IV, with the RA III slipping in between the base 400 and the RA IV.

Ram Air III

This engine had the large ports of the standard engine and used much more free-flowing cast iron exhaust manifolds.  The intake manifold was an iron semi-high-rise type, with a Quadrajet carburetor.  The camshaft was significantly hotter than the regular engine, too.  All in all, its 366 hp rating was probably fairly close, perhaps just a bit low.  Of course, the engine had an air breather assembly that sealed to the bottom of the hood, to allow the two hood scoops to be functional.  (See I Love Hood Scoops)

The engine used cast components and a two-bolt block, although it was setup for four-bolt mains.

Ram Air IV

Now you’re talking!  This thing was wonderful and had a ton of goodies.  The round-port cylinder heads were the most important feature, but add to that larger intake ports, tuliped valves, wild cam with 1.65:1 rocker arms, modified combustion chambers, plus the gorgeous exhaust manifolds and aluminum intake manifold.  Connecting rods and pistons were forged. The 370hp rating, a mere 4hp higher than the RA III, was indeed substantially below the true power peak.  (See Horsepower and Torque for a discussion of under-rated engines and true power estimates.)

Ram Air V

That’s ‘V’ as in ‘5’, as in ‘500’, as in ‘500 horsepower’!

Well, 500hp might be a bit of an exaggeration, but not necessarily.  This engine was of the ‘tunnel port’ design, featuring round intake and exhaust ports as big as sewer pipes.  It’s said that four different engines sizes were planned, 303cid, 366cid, 400cid and 428cid, with the 400 being the ‘street version’.  Some heads were manufactured, but the program died quickly when it became apparent that the muscle car trend was living on borrowed time.  And, yes, in the wonderful times we live in today, a mere search in your browser will yield at least one manufacturer of aftermarket aluminum Ram Air V heads.  Not inexpensive, mind you!

This is the Royal Bobcat Ram Air V GTO. The base color of the car is blue, with white as the accent color. It’s a great looking car, and I can see a custom ’69 styled like this but not in blue. Carousel Red, anyone?

Yeah, it looks just like the Ram Air III, but we have to have a pic of the RA IV, right?

The Ram Air IV exhaust ports were round and LARGE! This contributed to its high-rpm nature, and hp way above the factory rating of 370hp.

This is a fairly typical Pontiac combustion chamber.

Pontiac 455cid V8

The bore of the 428 was given an additional 0.030” and the stroke a more generous 0.21” to make the slightly-undersquare 455.

This thing was no high-revving engine.  There wasn’t an awful lot that was special about the ‘ordinary’ Pontiac 455 engines.  Good flowing heads, nice sized valves, cast internals, two-bolt mains, etc.  Good, but not remarkable. The introductory 1970 versions had 10.0:1 and 10.25:1 compression ratios.

What was remarkable were the high-performance versions of the 455.  These include the ’71 – ’72 HO versions, and especially the ’73 and ’74 Super Duty engines.

The ‘71 – ’72 HO engines had heads with round exhaust ports, like the Ram Air IV.  Compression ratios had dropped markedly, but the free-flowing heads more than made up for it.

455 HO

The 455 HO (High Output) was the low-compression bridge between the 1970 455 and the ’73 – ’74 Super Duty 455. It was the top 455 engine for 1971 and 1972. It had the normal cast components and 4-bolt main caps. Notably, it had round exhaust ports and intake ports that were 1/8″ taller than the regular ports. Compression ratio was 8.4:1, which was a bit higher than any of the other Pontiac engines.

Super Duty 455

This engine could be viewed as the final evolution of the 455 HO engine.  The heads not only had the round exhaust ports, but were marvels of cylinder head design, flowing air like a freakin’ wind tunnel!  The block had four-bolt mains, and even had provisions for converting to a dry sump!  The block was beefy, with additional bracing, and connecting rods and pistons were forged.  The crank was a cast, nodular iron piece. Connecting rods were heat treated, shotpeened and magnafluxed. Both the 1973 and the 1974 engines had an 8.4:1 compression ratio. The engine was going to use the hot RA IV ‘041’ cam, but emissions concerns dictated a milder cam. Super Duty intake ports moderately outflowed the RA IV or HO ports.

Firebird Trans Ams and Formulas were the sole recipients of the SD 455 engines, as the GTO was considered to be on the decline.  If you could have taken a SD 455 back to the height of the muscle car wars, in the late ‘60’s, this thing would have been a threat to virtually anything, being capable of running well into the 13’s.

Pontiac was known for having some attractive, free-slowing exhaust manifolds.

Super Duty 455 heads were not identical to the 455 HO heads, but they bore the same design philosophy.

The Top 400 Made as Much Power as the Top 455?

Well, yes; kind of.  Pontiac decided to hamstring the 455 when it was introduced in 1970.  Just utilizing the Ram Air IV heads would have resulted in 420hp, using the specific output of the 400 RA IV (0.925hp/in³).  But let’s consider that the RA IV, rated a mere 4hp more than the RA III, was indeed under-rated by Pontiac.  A more realistic value would conservatively be 400hp.  That means our RA IV 455 would be in the neighborhood of 455hp!  It’s a little hard to believe that it would exceed the output of the Chevy 454 LS6, but still, it would have been a real monster.  Some think that Pontiac didn’t want the warranty risk, which might have been a part of their thought.  A high rating like this might have brought undue attention of the type that is not welcomed.

Chrysler Corp. Engines

Chrysler came into 1964 well positioned in the performance field.  The little polyspherical 318 had already been around awhile, but this little gem would go on to outlive the muscle car era.  The 383 was also far from new, but it would be the bedrock of Dodge and Plymouth performance well into the 1970’s.  Then there was the 413, already in the process of being phased out, and its larger brother, the 426 wedge.

Hemispherical heads were put on the 426 block this year, but this would be a race-only engine until a street version appeared in 1966.  There was also the 361, which would be around for a few more years.  It wouldn’t be come anything more than a ‘base V8’ engine, though.

Chrysler Corp. LA-Series Engines

273cid V8

The 273 was the first member of the LA-series (“lower-A”) in 1964. It featured forged crankshaft and connecting rods, as well as mechanical lifters. This 180hp version was joined by a 235hp 4bbl version in 1965. 1966 saw the high water mark for the 273, with the top version making 275hp. This engine made 1.007 horsepower per cubic inch displacement, putting it in exclusive company. Intended for D/Stock racing, the engine did not carry a factory warranty.

The 273 had 2.50″ main bearings and 2.125″ rod bearings, with valves sized at 1.78″ (Int) and 1.50″ (Exh).

Dodge, Plymouth 318cid V8

This engine was borne in the Chrysler corp. ‘Polyspheric Head’ era, 1955 to 1958, being a member of the initial A-series engine family.  The 318 did yeoman’s duty for Dodge and Plymouth from 1957 until well after the muscle car era ended.  It was a ‘regular performance’ engine for most of its existence, although in its first couple of years it had versions that made as much as 290 hp.  In 1967 the 318 became a member of the LA-series engine family. The 318 was always a 2bbl engine. Like the 273 it had 2.50″ main bearings and 2.125″ rod bearings, with valves sized at 1.78″ (Int) and 1.50″ (Exh).

340cid V8

The 340cid V8 appeared in 1968 and was the performance member of the LA-engine series, utilizing nothing but 4bbl carburetion. That is, unless it was the 290hp version for the AAR ‘Cuda or Challenger T/A, which breathed through a 3 x 2bbl intake. With a bore of 4.04″, this was a 0.013″ increase over the 318cid V8, with an equal stroke of 3.31″. Valves were larger, at 2.02″ (Int) and 1.60 (Exh). The intakes were reduced to 1.88″ for 1972 and later engines. Also, compression ratios were higher than its LA-series cousins.

Chrysler 360cid V8

A 0.024″ stroke increase of the 340 and a 0.040″bore decrease resulted in the 360cid V8. Valves were equally sized, and seeing the same decrease in size in 1972. In 1974 the 360 took on a high-performance persona, its 245hp being quite competitive with similar sized engines in this low-compression wasteland. It saw extensive use in trucks, even into the next millennium. The 360 was almost the same displacement as the earlier 361, but was somewhat less oversquare than the 361 was. Recall that the 361 made up to 355hp (gross). The 361 was gone for five years when the 360 finally arrived.

Chrysler B and RB-Series Engines

361cid V8

Unlike the 383, which is detailed after this engine, the 361 ended up as a de-tuned ‘meh’ kind of an engine.  Maybe a little like the 318, but not nearly for as long.  Remember that this engine was introduced in 1958. Long gone were the 355hp fuel injected days, and the 310+ hp 2 x 4bbl days.  These were two-barrel, low-compression engines that no longer had a role in this high-performance era.  Such is the fate of many engines that were once noteworthy.

383cid V8

The venerable 383 had been released in ’59 as an ‘RB’ block engine but was made a ‘B’ block the following year.  It shared the valve sizes of the 350 and 361 engines.

1968 would be the year the 383 received some upgrades, most importantly new cylinder heads, with 2.08”/1.74” valves.  These heads also had better flowing ports and were similar to 440 heads.  A more aggressive cam was used, as was a high-rise cast iron intake manifold.  In 1970, the Carter 4bbl would be replaced by a Holley.

It’s important to note that the 383 was one of the most important engines the Chrysler corporation had.  It was used by Chrysler, DeSoto, Imperial, Dodge and Plymouth.  Unlike many ‘top rung’ performance engines, it was never really relegated to low-performance-only applications when larger, higher output engines came along.  In fact, it outlived the 413, 426W and the 426 hemi, not to mention the 350 and the 361.  In its ’68 and later, 335hp form, it earned more than its share of ‘street cred’.  Definitely one engine that punched over its weight.

Here’s a view of the combustion chamber of an open chamber 383 head.

The fact that the 383 only gained 10hp with the 2.08″/1.74″ heads has always bothered me. I know that this engine punched above its weight, but a measly 10hp? I’m thinking maybe someone should call BS on this!

413cid V8

The Fate of the 413 was a bit kinder than that of its Chrysler siblings.  No, there would be no more 410hp and 420hp dual-quad versions, but it still had one good year left as an ‘nearly 400hp’ engine, thanks to its two Carter 4bbl carburetors.  Its compression ratios weren’t emaciated, like those of the 361, and it was never to be saddled with a two-barrel carb.  The legacy it left behind, with its wild intakes and often funky exhaust manifolds, became an essential part of the pre-muscle car performance era.

426cid Wedge V8

This engine was a monster.  Huge ports and valves, high compression, plenty of carburetion.  The ‘wimpy’ version of it made 365hp and 470 lb.-ft. of torque.  Even in its next-to-last year, you could still get the 425hp, 13.5:1, dual 4bbl version.  This engine was never relegated to ‘base V8’ duty, nope, nope, nope.

When the 426 Wedge bowed out, the 426 Street Hemi was waiting in the wings, for its 1966 model year introduction.  The Hemi was essentially this block with new heads.  The muscle car scene would never be the same after ‘the Elephant’ arrived on the street.

See the 1946 through 1963 Engine Development by Automaker section of Early US Automotive History for more 426W information.

426cid Hemi V8

There were some fantastic engines designed and built during this era, engines from most of the automakers who fielded muscle cars.  The 426 Hemi was undoubtedly at the top of the list.

The 426 was one of the ‘RB’ block engines, being related to the 383, 400, 413, and the 426 wedge.  It shared the 3.75” stroke of the family, with a 4.250” bore.  The RB engine deck height was 10.725”, while that of the B block engines was 9.98”.  Bore spacing was specified as a generous 4.80”.  Connecting rod length was 6.760” for all RB engines.

The Nay-Sayers

The thought of it saddens me, but there may be some of you who are saying something like “I think the Chevy L88 was a better engine …”. Yeah, there were other marvelous engines, but none that had the combination of sweet components (think ‘high-rise’, ‘dual’, ‘solid’, ‘forged’, ‘NHRA’, NASCAR’, and last of all, ‘hemispheric’). No other engine was the combination of all this, was fairly streetable, and readily available. Try taking your L88 on a Saturday night cruise when it’s still 95 degrees outside!

My Momma was a Race Engine

Most of us know that the ‘street’ Hemi was developed from the race Hemi.  While this is true, there’s a lot more to the story.

In 1964 Chrysler introduced two different versions of their new racing engine.  The NASCAR version sported a single 4bbl carburetor, in accordance with NASCAR regulations, while the NHRA version had dual 4bbl carbs on a magnesium cross-ram intake manifold.

The 1964 Daytona 500 saw hemi-powered cars take the first three places.  Ford had been doing extremely well in NASCAR, thanks to their 427.  The Hemi was certainly going to change the balance of power, and Ford wasn’t going to take it laying down.

Ford lobbied NASCAR, the result of which was it was ruled that non-production, race-only engines were no longer permitted.  Engines had to be homologated, which, in this case, meant that at least 500 engines had to be sold to the public, being factory installed in any vehicle the automaker offered.

Ford Responds

Ford had already undergone a crash engineering exercise to modify their 427 to allow it to reach or exceed the Hemi horsepower levels.  This, of course, was the SOHC 427.  It was never installed in a factory vehicle, and it would never race NASCAR.  The homologation edict caused Ford to rethink the whole thing and to stop production of the SOHC.  Luckily, Chrysler chose the other option, that is, to go ahead and make the engine available to the buying public.   They didn’t stop at the required 500 installed engines, either.  The Hemi was available to anyone with enough of a bank account to afford the extra bucks for it.  You could count on the upgrade to the 426 to cost at least $500, depending on the model and base engine.  A ’67 Charger only cost just over three grand, so an extra $500 – $700 wasn’t chump change.

Gotta Have Lots of Carburetion

Behold…1200 cfm of carburetion, needed to supply the hungry 426.  Part of the beauty of a dual quad setup like this is that the carburetor barrels are more evenly distributed and closer to the ports they feed.  Yeah, the plenum chamber serves to equalize the flows to the eight cylinders, but this is one sweet setup for an engine that actually needs this amount of flow at high rpm.

The differences between the race and street Hemis were relatively few.  Race engines had both cast iron and aluminum heads, while those of the street engine were exclusively iron.  Cams were different.  Both used solid lifters.  Manifolds were different, of course, with the race engines using headers rather than exhaust manifolds.  Other small differences here and there, but this sums it up.

You have to remember that Chrysler did not initially intend for there to be a street version of this engine.  It’s only the new homologation requirements that led them in that direction.  They could have done what Ford did with their 427 SOHC.  Thank goodness they didn’t!

Beefy Hardware

These beefy, forged rods are used by the 426.  All of the hardware was top-rated.  The exhaust manifolds were sculpted and flowed like headers, unlike most performance engines, which often had manifolds indistinguishable from those on mom’s big-engine station wagon.

Its cylinder heads were undoubtedly the most important and interesting part of a hemi engine.  After all, the word “Hemi” refers to “hemispherical”, which is the shape of the combustion chambers.

The huge valves (2.25” Intake, 1.94” Exhaust) were possible, even with a 4.25” bore, because the valve size wasn’t specifically limited by the bore size.  Trying to cram these huge valves into a conventional wedge combustion chamber would require a bore size of probably close to 4.50”.

Funky Heads and Domed Pistons

The deep combustion chambers had to be machined, which contributed to the cost of the engine.  The pistons were domed, to achieve the proper compression ratio.  The compression ratio of the street Hemi was a manageable 10.25:1, not nearly as high as most of the other 425+ hp engines of the era.  Of course, the race Hemi engines had higher compression ratios, achieved by the use of pistons with larger domes.

The separated intake and exhaust valves for each cylinder mandated the use of shaft mounted rocker arms, something that the industry had been moving away from since the introduction of stud mounted, stamped steel rocker arms the Chevy 265 introduced in 1955.  The 426 setup was beefy, and it was expensive to manufacture.

Not only did the street engines have the same valve sizes as the race engines, but they also had the same port sizes.  These were big enough to swallow your Shih Tzu.

Dodge and Plymouth, but not Chrysler?

It’s kind of funny that Chrysler itself didn’t use the Hemi, but long before ’66, when the street Hemi appeared, Chrysler had been focusing solely on larger, luxury cars.  Mild versions of the 383 and 440 were their go-to engines.  The 426 was way too wild.

I have to say that the Hemi was one of the most attractive engines of all time.  Both the orange oval air breather and the round chromed one were fabulous, and the large valve covers with the spark plug passages were just plain crazy cool.  Some versions were chromed, and some black crinkle painted.  Whatever the combination, nothing was as cool and sexy as a 426 Hemi nestled in the engine compartment!

440cid V8

The 440 was the Chrysler ‘big’ engine, comparable to the 454’s, 455’s and 428’s of the competition.  Released in 1966, it was a 350/365 hp engine.

The next year, 1967, the engine would receive heads with larger ports and exhaust valves, and the highest output version would have its output bumped up to 375 hp.  The intake and carb were new, as was he more aggressive cam.

It would be midyear 1969 when the 440 cranked the dial all the way to ‘10’ (or ‘11’, if you’re a Spinal Tap fan).  This was the 440 topped with an aluminum intake manifold, on which were mounted three Holley 2bbl carburetors.  For good measure, the compression ratio was bumped up .4, to 10.5:1.

1968 and later 440 heads were of the open chamber type.

440 Six-Pack

This engine has an interesting story.  Chrysler wanted a performance engine that was placed between the 440 4bbl and the 426 Hemi.  It’s also been stated a bit differently, that they wanted an engine approaching the 426 in performance, but not nearly as expensive.  Either way, what they ended up was the wonderful 440 Six-Pack.  Actually, that was the Dodge name for the engine, the Plymouth designation being 440 6-Barrel.

The engine was offered in mid-1969 as the A12 option on Plymouth Road Runners and Dodge Super Bees.  This option also provided upgraded brakes and cooling system, and a lift-off fiberglass hood that had a raised scoop big enough to be a danger to any small child who wandered too close.  No hinges, mind you; this hood was lift-off only.   Can you say ‘Bad-Ass’?

The center 350 cfm carb supplied air and fuel for ‘normal’, every-day driving.  Pressing the accelerator to the floorboard resulted in the two end, 500 cfm carbs opening up and a bunch of noise coming from both ends of the car. It should be noted that this did not equate to 1,350 cfm. The rating for 2bbl carburetors is somewhat different from 4bbl carbs, and the total flow of these three carburetors is about 954 cfm. Still plenty healthy!

Also standard with the A12 package were 4.10:1 gears, beefy connecting rods, and a special cam.  It’s undeniable that the 440 Six Pack got a lot of respect on the street, regardless of what the other guy might have been driving.  For ’70 and ’71 (last year of Six Pack), the engine became a standalone option, not tied to any package like the A12, and therefore available in more Dodge and Plymouth models.

This is one attractive engine, and 390hp to boot!

Ford Engines

Ford came into 1964 with their still new 427 and the venerable 390, which appeared in 1961.  This would be the last year for the short-lived 260cid V8, and the 352 was in its seventh year.  The sweet little 289 was still new, making a very respectable 271hp in its performance version.

M-E-L Series

There’s not much to talk about here.  The unremarkable, Lincoln-only 430 became the unremarkable, Lincoln-only 462 in 1966.  The original members of the MEL series, the 383 and the 410, were long dead by now.  The 462 was the last of the MEL series, which had been introduced in 1958.

Here’s the largest member of the M-E-L series, the Lincoln 462. Kinda, uh, unremarkable. It’s a 0.08″ bore increase and 0.13″ stroke increase over the 430.

Ford 90-Degree Engine Series

This is the Ford Motor Company small block family of engines, unimaginatively named from the 90° angle of the cylinder banks. Don’t let the fact that pretty much all domestic V8 engines have this cylinder bank angle confuse you. The series started in 1962, with the little 221cid V8. (See 1946 through 1963 Engine Development by Automaker section of Early US Automotive History)

289cid V8

1964 would be the last year for the unremarkable 260cid V8.  The 289 would be around through 1968, which meant the 271hp 289 HiPo K-code was also available.

To recap, from the 1946 through 1963 Engine Development by Automaker section:

With a Holley 4bbl and moderate 10.5:1 compression, this little screamer made 271hp at 6,000 rpm.

This engine had a higher compression ratio than the garden variety 289, and it also received a hotter cam and a larger (595cfm) Autolite carburetor.  The block was specially selected to be free of flaws, and then received thicker main bearing caps.  The connecting rods received larger bolts.  The crankshaft was cast from 80% nodular iron, for greater high-rpm reliability.  Even the pulleys and fan were designed for high-rpm operation!

The 289 HiPo was targeted for the Fairlane and was also offered as an optional engine for the Mustang, when it was introduced.  A smaller, lighter car with a smaller, lighter high-output engine is a sweet combination.  As the decade progressed, and the ‘more cubes are better’ mentality prevailed, small, high revving engines like this were only sold in small numbers.  Unfortunately, it’s generally more cost effective to manufacture, and purchase, an engine that makes power at a lower engine speed, thanks to larger displacement, relative to a little high-rpm screamer like the 289 HiPo.

Ford 302cid V8

Introduced in 1968, this was not a high-performance engine.  It was borne of a 0.130” stroke increase of the 289.  The resulting bore and stroke are familiar to any Ford enthusiast, 4.00” x 3.00”.  Valves were 1.78”/1.45”.

The first year saw both 2bbl and 4bbl versions of the 302, but after that, they were strictly 2bbl versions for quite a few years.  The engine was used for ‘base V8’ engine duty, with the 289 overlapping it just for ’68.

Why So Oversquare?

The 302 was a hugely oversquare design with its 4.00″ bore and 3.00″ stroke. Yeah, this made sense for the Boss version (and Chevy’s DZ 302), but the vast majority of Ford 302 engines were of the more mundane variety. Why so much more oversquare than most engines?

I think this was more the result of happenstance than anything else. The original member of the family, the 260, had a 3.80″ bore and 2.87″ stroke, for a 1.324 bore/stroke ratio. The ratio for the 289 was 1.394, with its 4.00″ bore and 2.87″ stroke. The 302, of course, saw the stroke increase to an even 3.00″; this resulted in a 1.33 B/S ratio. Clearly, the 289 cid was more oversquare than the 302 was! For comparison, the Chevrolet small block engines tended to have B/S ratios of less than 1.30.

Ford Boss 302

This 1969 – 1970 engine was born of the intention of Ford to participate in SCCA Trans-Am racing, with their 5-liter displacement limit.  Ford designed a new, big-port, big-valve head for the 302.

The ports were far larger than practical for an engine of this displacement, and the valves, at 2.23”/1.72”, were gargantuan.  Additionally, the valves were canted.  The intake valve had a side angle of 4°15’, with a back tilt of 9°30’.  The Exhaust valve had the same back tilt, but a 3° side angle.  This was substantially less pronounced than a Chevy Mark IV head.  The intake valves were downsized a bit, to 2.19”, for the second and last year, 1970.

If you’re not familiar with degrees, minutes and seconds, here’s a refresher.  A minute is 1/60^th of a degree, and a second is 1/60^th of a minute.  Minutes are designated by single quotes (‘) and seconds by double (“).  Naturally, one second is 1/3600^th of a degree.  Easy-Peasy!

The Boss block had four-bolt mains, with the same bearing sizes as the 302.  All internals, including pistons, were forged.  Atop the aluminum intake manifold sat a 780 cfm Holley carburetor.  Ford had to make the engine available to the public to homologate it for SCCA racing, so it was available in the Boss 302 Mustang for 1969, and then added to the Cougar Eliminator for 1970.

“…it really was a 400hp engine…”

No, it wasn’t.  The Boss 302 has long been rumored to produce vastly more horsepower than the factory rating.  One source references a Ford statement that the engine dyno tested at 314 hp.  One magazine dyno tested a ‘mostly stock’ Boss, with headers, and got about 375 hp.  I could accept that the engine, as released, might dyno some 30 to 35 hp higher than its rated 290 hp, and that good headers and other tweaking could put you up to 350 hp or higher.  I’m sure the thing was good for 400+ hp with some good, old-fashioned hot-rodding techniques, too.  Just not out-of-the-box.

These are almost ridiculously large ports for 302 cubic inches!

Ford 351W

The 351 Windsor is kind of the red-headed stepchild of the Ford 90-Degree family.  The block was already at its practical limit for enlarging, having smallish 4.38” bore centers.  It couldn’t be bored or stroked any further.  The solution?  Leave it as-is and use a different engine series to fill this niche.  Well, that could have been what they did, but instead, Ford increased the deck height of the 90-Degree block, reinforcing it in key areas in the process.  The 8.206” deck height of the 289 and 302 was increased to 9.50” for the 351W.  At the same time, the main bearings increased from 2.25” to 2.9” and the rod bearings from 2.13” to 2.60”.  The connecting rod length was increased from the 289/302’s 5.15” to 5.954”.

What’s with the ‘Dubya’?

This engine was manufactured in Windsor, Ontario, which is south of Detroit, just across the Detroit River.  Yes, South—check the map.  The ‘W’, for Windsor, is to differentiate the engine from the other Ford 351 engine, the 351C (for Cleveland).  The two engines shared nothing and were members of two different Ford engine families.  Gotta love Ford’s penchant for having different engines that were incredibly close in displacement.

The year of its introduction, 1969, saw the highest horsepower rating for the 351W, at 290hp at a surprisingly high 5,800 rpm.  This would be the last 4bbl 351W, and it was available in such models as Fairlane, Mustang, Falcon, Cougar and Montego.

Ford FE Engine Series

The Ford-Edsel engine family had been introduced in 1958, with the 332 and 352cid V8s. You might recall from the Pre-Muscle Car Engines that the top 352 made a whopping 360hp!

352cid V8

This engine would be around through 1966, having been introduced in 1958.  Its 360 hp days were long behind it, and for the remainder it was relegated to ‘base V8’ duty.  See See 1946 through 1963 Engine Development by Automaker section of Early US Automotive History for more information. The 352, as a member of the Ford Truck (FT) family, would see duty into the late 1970’s.

390cid V8

The venerable 390 would continue to be a viable performance engine option throughout the decade.  There would be no more 375 hp or 401 hp versions, though, but the engine would be available in versions making up to 320 hp. 

The 390 was the product of a bore and stroke of the 352 in 1961.  It had the smallish 2.04”/1.57” valves of the 332 and 352 engines.  The hottest earlier versions of the engine had triple 2bbl induction.  See See 1946 through 1963 Engine Development by Automaker section of Early US Automotive History for more information.

Mercury 410cid V8

This engine was available from Mercury for just two years, 1966 and 1967.  It was a 390 with an additional 0.200 in. stroke.  I can only guess that Merc wanted a larger displacement than the 390, but the engine was certainly short-lived. The sole version made 330hp.

427cid V8

This was the bad ass of the FE family, with its high revving, high output and its racing heritage.  It was a star, no question.  The 428 and 429 that would follow would never possess the gravitas, or the pure sex appeal of the 427.  As with the 390, see See 1946 through 1963 Engine Development by Automaker section of Early US Automotive History for more information.

Ford 427 SOHC

This engine was intended to be an answer to the dominance of the ’64 Chrysler 426 Hemi in NASCAR competition.  You will recall that Chrysler was required to homologate the 426 by offering sufficient numbers of Hemi powered cars to the public.  Ford must have had the same idea with the 427 ‘cammer’.

How was this engine going to aid in the battle against the hemi cars?  Ford knew that the 426 breathed incredibly well and that trying to produce an engine that breathed significantly better was not realistic.  What was realistic, though, was to design an engine, based on an existing platform, that would move more air and make more power by going higher in rpm.  Greater engine speed, say, 15% higher rpms, keeping the same torque, means 15% more horsepower.  That’s the difference between a 600hp engine and one that makes 690 hp.

But How Do You Do That?

How do you increase engine speed?  You address the one factor that, more than anything else, limits the speed of an engine — the valve train.  Overhead cams (one per bank, 2 valves per cylinder) eliminate much of the valve train mass, and therefore its inertia.  This allowed the ‘cammer’ to achieve 7,500+ rpms, and its free-flowing port and valves supported making power at these higher engine speeds.

In designing the SOHC, Ford wisely tried to use as much existing, off-the-shelf, hardware as possible.  One thing that was definitely not off-the-shelf was the huge, gorgeous valve covers.  They were finned, more for aesthetics than for anything else, I suspect.  And they were made from magnesium!

So, what happened?  The engine never reached the point of being homologated, and a small number of engines were sold over the counter.  You could buy a lower to mid-priced Ford car for what a 427 SOHC cost, some $2,500!  Bill France, the owner of NASCAR, didn’t like the mere idea of overhead cams, as he considered them “too European”.  Thus, what might have become a legendary rivalry was dead.

The SOHC used chains to turn the two cam sprockets.  The huge (2.25”) intake valves had hollow stems, and the 1.90” exhaust valves were designed with sodium filled stems, to aid in heat transfer.

Hey, if you’re at a cruise in or some such event, and someone pops the hood of their Ford to reveal a 427 SOHC, you might as well just quietly lower the hood of your car and just forget about it.  Nothing, I mean nothing, is going to draw the attention like this engine.

427 SOHC Output

616hp at 7,500 rpm (Holley 4V), 657hp at 7,500 rpm (2 x Holley 4V, code “M”); 12.1:1 compression ratio

Note how the cam chain is driven off of the gear that’s placed at what would otherwise be the camshaft location for the regular 427.

428cid V8

The 428 earned its stripes in its Cobra Jet and Super Cobra Jet versions.  The engine became more associated with the Mustang than any other FoMoCo model.

The block of the 428 may not have been christened with the term ‘Y-block’, but it was still a design that had rather long block skirts.  This is very obvious when comparing to a Chevy block of the same era.  It’s not whether one is better than the other, just that the long skirts represent dated engine design principles, and that they tend to be heavier.

428 Cobra Jet and Super Cobra Jet

Just what were these two engines?  Or were they more than engines?  Starting in 1969, if you ordered a Mustang with 3.91:1 or 4:30:1 gears, you also received the SCJ engine.  The primary difference between the SCJ 428 and the plain 428 was the rotating/reciprocating assembly, namely, crank, rods, rod pins, and pistons.  All 428 engines, including CJ and SCJ, used cast pistons.  The SCJ engines, with their heavier connecting rod cap bolts, were externally balanced. 

The 428 (non-CJ/SCJ) used the same 2.04”/1.57” valves of all of the other FE engines, the 332, 352, 360, 361, 390, 406, 410, but not the 427.  The CJ/SCJ versions had heads with larger ports and larger, 2.04”/1.57” valves.  These were far from ‘small’, but when you consider that the regular 396 had 2.06”/1.72” valves, and a ’68 383 had 2.08”/1.74” valves, they certainly weren’t huge.  As a final point, the ’62 – ’63 Ford 406 had valves sized at 2.09”/1.66”.

It’s kind of interesting how the rearend gear ratios are tied to the engine, as most sources seem to state “…if you ordered a Mustang with 3.91:1 or 4:30:1 gears, you also received the SCJ engine”, or something close to this. I have to think that the reasoning was if you’re specifying these steep gears, you are doing so for the reason of performance, and you are going to be subjecting the engine to some high revs, thus warranting the heavy-duty internal components.

The 428 Cobra Jet/Super Cobra Jet Horsepower Dilemma

It should be kept in mind that the 428 was the end of the FE engine family, introduced in 1958.  The 428 can be viewed in relation to its siblings as a bored 410, a stroked 406, or a bored and stroked 390.

The 390 made 375hp with a 4bbl, and 401hp with a 3 x 2bbl setup.  The 406 was good for 385hp and 405hp, respectively, with the same carb configurations.

If we’re really honest, we could say that it’s disappointing that the 428 CJ/SCJ didn’t make over 400 hp.  Pontiac had a 428 that was a large-car engine that made 405hp with a 4bbl carb.  With the hottest 390 and 406’s making more than 0.95hp/in³, the 428 would have been good for 406hp with the same carburetion.  I dunno.  Could that be the real reason that Ford didn’t rate the 428 horsepower accurately?  ‘Rate it low and let the rumor mill assign an overly high value’?

In a February 1967 article, Motor Trend referred to the 428 of the Shelby GT500 as “The 428 is a passenger-car engine, and nearly $1000 cheaper than the 427. Few people would be happy with the 427 unless they were racing it.”.

Some sources state that the great Roger Huntington put the 428’s actual output at 410hp.  Hot Rod (see above) dyno tested a 428 at 365hp.  ‘Driving’ (www.driving.ca) alluded to an unspecified 428 dyno test resulting in 450hp.  Looking at other engines that were rated at 425 – 450hp, and that would be supported by dyno testing, I just don’t see that in the ‘makeup’ of the 428.  Nor, frankly, did we see that in the performance of CJ and SCJ Mustangs.  They were fast, but not 450hp fast!  A 428 SCJ with 4.10:1 gears and 450hp should have shown an LS-6 450hp Chevelle its taillights, being some 300 lb. lighter.  But that wasn’t the case, was it?

Big Block Comparo

This chart gives you something to think about.  It’s just another set of data points.

It shows that the 428’s valve area per cylinder, at 0.1041in²/in³, is less than the other listed engines, which is in direct relation to valve size (naturally).  Simply put, with 5.57 square inches of valve area per cylinder, and 53.3 cubic inches per cylinder, each of those cubic inches of displacement is ‘supported by’ 0.1041 square inches of valve area (intake and exhaust).  Compare this to the Ford 429, at 0.1175 in²/in³.  The difference is in the range of 13%; not insignificant.  Compared to the 426 Hemi, the difference is a full 25%!

My whole point is just that this is something to think about.  There is such a thing as valves being too large, and some would say that the Boss 302, Boss 429 and 351C are examples of this.  Nevertheless, the Ford 428 did not have the inherent breathing ability as many of its contemporaries, at least regarding valve sizes.

There have been many reasons suggested as to why Ford chose to rate the 428 this way.  What seems odd is that the underrating was specific to the 428, not the 390 or the 427 or the 429 (yeah, ignoring Boss 429, but that’s a different story).  It certainly didn’t fool the NHRA, as 428 cars were bumped to a different class.  Why, Ford, why?!  Another example of corporate dumbassery? I dunno.

Ford 385 Engine Series

This engine family was introduced in 1968 and would see production for two decades.  It consisted of the 370 (truck only), 429 and 460.  The 429 would earn its place in automotive history, while the 460, which would never exceed 0.80 hp/in³, would be a medium-performance, large car engine.  The engines shared a 4.36” bore, one of the industry’s largest.

These engines would obsolete the 390, 427 and 428, and would see duty in larger cars, performance cars and trucks.  Newer casting techniques, and the obsoleting of long block skirts, allowed the 385 engines to each be a few hundred pounds lighter than an FE engine.  Head design had been rethought, too.  The 385 engines had large ports and large valves that were canted, similar to the Chevy Mark IV engine family.  Bore centers were also substantially increased, allowing the 385 to grow in displacement, should the factory decide to take this route.  These engines were hugely over-square, which was rather unusual.

427, 428, 429, 430, 431…?

Well, maybe not 430 and 431.  But yes, Ford had these three (rounded) engine sizes.  In fact, the engines available in 1969 were the 390, 427, 428 and 429.  The 427 was a high-performance engine that was expensive to manufacture and not well suited for large-scale production.  The 390 and the 428 were heavy engines that had heads that reflected earlier design thoughts.  The 429 would be less expensive to manufacture, lighter, and offer greater performance potential, as well as emissions compliance potential.  It’s just kind of odd that the engines were so close in displacement.  Of course, they all had different bore, strokes and bore spacing values.

429cid V8

The 429 debuted in 1968, being an optional engine for the Thunderbird.  Its 360hp was equal to the output of the 428 Super Cobra Jet, yet it arrived at 4,600 rpm versus the 428’s 5,400 rpm.  This was with similar compression ratios and carburetion.

The garden variety 429’s had a valve size of 2.08”/1.66”, while the Cobra Jet and Super Cobra Jet versions had heads with sizes of 2.25”/1.72”.  The valves were canted by 5°/9.5° for the intake (two axes of tilt), and 4° for the exhaust.  These values were much less than those for the Chevy Mark IV (396/427/454) heads.  Bore and stroke were a very over-square 4.36” x 3.59”.

‘Poly’ What?

Well, maybe I’m just too simple, but I don’t like the term “poly angle” that is sometimes applied to the 429/460 heads.  I’ve never seen this term applied to the Chevy Mark IV, and their valve angles are more pronounced than that of the Ford 385 engines.  These were canted valves, nothing more, nothing less.

429/460 heads came as both closed chamber type and open chamber type.  The ultimate compression ratio was determined by the combustion chamber volume (larger with open chamber) and the volume of the piston pop-up, if present. The closed chamber heads had substantial ‘quench/squish’ areas.

The open chamber heads were generally found on 2bbl and lower performance heads, with lower compression ratios.

The image of the 429 block will give you some perspective on the block wall thickness.  Compare this to the image of the 428 block.  Also note the difference in how far the block sides extend down.

429 Cobra Jet and Super Cobra Jet Engines

These engines not only had heads with larger valves, these heads also had larger ports.  The internals weren’t much different from the non-CJ/non-SCJ versions…Crank and rods were cast, as were the pistons in the CJ; SCJ got forged pistons.  Both engines had 11.3:1 compression ratios.

Camshafts were different, with the CJ having a hydraulic lifter type and the SCJ a solid lifter type.  When it came to carburetion, the CJ and SCJ couldn’t be more different.  The CJ actually used a GM Rochester Quadrajet carburetor!  Yep, that’s right.  Ford used a General Motors carburetor on the CJ!  The SCJ used a Holley 4bbl carb.

‘Chevy Carb’ on a Ford! Are you Smokin’ Dope?

‘Yes’ and ‘no’.  Yes, to the former and no to the latter, that is.  I’m not sure how this came about, but it most certainly did happen.  Ford, of course, had a long, long history of using Holley carburetors, even for non-production engines.  The SCJ got a Holley, why not the CJ?  That’s the $64,000 question.  One could speculate, but hard evidence is difficult to come by.

The Q-Jet was the industry’s first spread-bore carburetor and was a pretty good compromise between everyday mileage and efficiency and open-throttle power.

Example of a GM Quadrajet carburetor.  Primary bores were 1.375” and secondary were 2.25”.  Most were rated at 750 cfm.

The ‘Q-Jet’ was a spread bore carb, with unequal size primaries and secondaries.  The smallish primary barrels provided high airspeed and a well-mixed air/fuel mixture, as well as a strong vacuum signal for metering.  The huge secondaries were able to supply the air/fuel needs of a large engine at wide open throttle.

They were known as being a bit finicky, but the resources today are great, and anyone with a Q-Jet carb has all the information they need to allow it to perform flawlessly.

460cid V8

The 460 saw its first use in the ’68 Lincoln Continental Mk III.  It would obsolete the MEL 462cid V8 engine.  It would be 1972 for Mercury and 1973 for Ford, when the engine was made widely available or multiple models.  Interestingly, the 460 would be replaced by the 400cid V8 of the 335 Series engine family, due to the new Corporate Average Fuel Efficiency (CAFE) standards.  You can thank the old farts in D.C for this.  The 460 would be exclusively a large car engine.

Boss 429

This term refers to either the 1969/70 Mustang model or the engine powering it.  We’re interested in the engine.

If you think about it, the wildly over-square nature of the 385 series engines actually makes some sense when focusing on the Boss 429.  Of course, only a mere handful of these engines were ever built, and for each one, there were thousands of more mundane 429s and 460 made.

The sole purpose of this engine was to help FoMoCo win NASCAR races.  In a sense it was the heir to the 427 SOHC.  To be allowed to race, the engine had to be homologated, or made available to the buying public in sufficient numbers.  That magic number was 500 engines, though they could be installed in Ford models other than the Mustang.  Two engines were installed in Cougars, but these were special circumstances, being factory-built for two drag racers.

The real magic of the Boss 429 lay in its cylinder heads.  These aluminum heads had huge valves and ports, featuring semi-hemispherical combustion chambers.  Ford called them ‘crescent’ shaped.  All of the engine internals were forged, naturally.  The block itself was somewhat different in that the block and the heads had their own cooling circuits.  This was known as a ‘dry dock’ method.  Passages between the block and heads were sealed with O-rings, and the head gaskets were used only to seal the cylinders.  It was felt that the dry-dock method could provide more effective cooling.

The valves themselves were huge, at 2.28” and 1.90”.  The valve covers were cast in aluminum and provided for the passage of the spark plug wires.  Carburetion was handled by a 735cfm Holley.

Ford 335 Engine Series

351 Cleveland

This Ford engine family consisted of the 351 Cleveland, Boss 351, 351C Cobra Jet, and the utterly unremarkable 400.

The 351C, named for the Cleveland Ford Plant, was the beneficiary of the cylinder heads developed for the Boss 302.  The heads were actually very, very similar. The ‘335’ itself was based on the target size of the first member of the family. Or so it’s claimed. With Ford, who the heck knows?

Ford had gotten behind the 8 ball with their small block engine offerings. The Windsor plant could not keep up with the demand for 351cid engines. What to do? Create a new 351, of course! That’s exactly what Ford did with their 351 Cleveland engine.

The 351’C’ shared the bore and stroke of the Windsor engine, but little else. The heads were quite similar to those of the Boss 302. The block was lower and wider, with a deck height of 9.206″. Heads were distinguished by application, either 2bbl or 4bbl, with the 4bbl heads having cavernous ports and valves. 2bbl valves were 2.04″/1.65″, with the 4bbl being 2.19″/1.71″. Both engines used hydraulic cams (4bbl hotter) and featured nodular iron crankshafts.

Motor Trend stated: “…though the four-barrel heads and valves may have been too much of a good thing, at least for responsive street performance.” This was in all likelihood true. Compression ratio of the 4bbl heads was a high 11.0:1.

Boss 351

1971 saw the demise of the Boss 302 and the Boss 429. Ford decided to create the Boss 351, based on the Cleveland engine, that would end up being a one-year-only option. This special ‘C’ engine received 4-bolt main caps and forged pistons. A high lift, high duration mechanical cam was part of the picture, as were numerous upgrades to the valvetrain, intended to ensure reliability at high rpms.

An aluminum spread-bore intake manifold was used with the Autolite 4300-D spread-bore carb, rated at 715cfm.

Motherly Big Valves and Ports

The Ford engines with overly large valves and ports, specifically the Boss 302 and Boss 351, have always seemed to me to have been an exercise in excess. As discussed in Horsepower and Torque, these big-valve engines were among those that were under-rated by their factories. Both the Boss 302 and Boss 351 engines were indeed under-rated by some 50 to 60 horsepower, although the actual power numbers aren’t exactly clear. 375hp+ with headers seems to be reasonable for each of these engines. Ford was probably the one company who tended to under-rate their mid and late 1960’s engines more than anyone else.

351 Cobra Jet

This engine arrived in late 1971. It was a mildly hopped-up 351C 4bbl, with a low 9.0:1 compression ratio.

The Ford 351 Saga

Not to belabor a point, but…

The confusion between Ford’s 351W and 351C is epic. I mean, isn’t life confusing enough without unnecessary corporate dumbassery? I sure think so. Back in 1970 we had Tricky Dick, Watergate and the Vietnam war. Today it’s an ex-President who thinks he actually won the election and a President who can’t seem to string three coherent words together. Oh, and this COVOID-19 shit show.

The confusion between these two engines will never end. Ever. Here, some five decades later, the confusion is as complete as it has ever been. Much present-day documentation (printed and electronic) seems to struggle with this, too, often just ignoring whether a particular 351 is a ‘C’ or a ‘W’!

Finally, look at the crap-load of different 351 ‘W’ and ‘C’ 2bbl engines that were available in the early 1970’s. The large-port ‘C’ engines didn’t seem to perform much differently at all than their smaller-port ‘W’ cousins.

Yeah, someday the crap show that is our executive branch circus will be history, but we’ll still be confused about the 351 ‘W’ and ‘C’ engines!