The Pontiac V8 was one of General Motors’ most versatile engines, serving the corporation well for more than 25 years. Here’s where it all began in 1955.
Among the General Motors divisions, Pontiac was rather late to the game in offering an overhead-valve V8. Cadillac and Olds rolled out their new V8s in 1949, while Buick’s Nailhead V8 (read our feature here) arrived in 1953. Pontiac delayed its OHV V8 until 1955, the same year the all-new Chevrolet V8 appeared. And partly as a result, the small-block has always overshadowed the Pontiac among performance enthusiasts. That’s a bit of a shame, as the Pontiac is a worthy engine in its own right, and a fascinating one.
The development of the Pontiac V8 began in 1946, as the division at first explored the possibilities for an L-head configuration (unrelated to the Oakland-based V8 briefly used by Pontiac in 1932, reportedly). But the superior characteristics of the overhead-valve layout, including greater breathing potential and a more compact combustion chamber, soon won out. The eventual design took some cues from the previous overhead V8s of Cadillac, Olds, and Buick, but also had some distinctive features of its own, as we’ll see.
Originally scheduled for a 1953 introduction but then pushed back to 1955, the new powerplant was branded at rollout as the Strato-Streak V8. (Later names included Tempest and Trophy.) Management originally planned to discontinue the old 268 CID Pontiac L-head straight eight and leave the 239 CID L-head six in production alongside the new V8, but then, in a leap into modernity, decided to offer the V8 as the sole engine across the board.
With an oversquare bore of 3.75 inches and stroke of 3.25 inches, the initial displacement was 287 cubic inches, but the generous 4.620-inch bore centers left plenty of room for displacement increases. The engine was soon upsized to 317 cubic inches for 1956, and by 1970 it eventually reached a whopping 455 CID. Unlike the V8s from other carmakers, there is no “small-block” or “big-block” distinction. All Pontiac V8s are based on the original 1955 architecture, regardless of displacement.
The small-block Chevy V8 is known everywhere for its stamped rocker-arm, ball-pivot valvetrain setup, but as most every gearhead knows, the low-cost, high-rpm innovation originated at Pontiac, where it was developed by chassis engineer Clayton Leach. While it shares no part numbers with Chevy, the ’55 Pontiac version is similar, but with a wrinkle or two (above). Here the rocker arm is lubricated via a hollow rocker stud and an oil passage in the cylinder head. Later on, Pontiac would drop this arrangement and adopt the more familiar hollow-pushrod system employed by Chevrolet. Clatter-free hydraulic lifters were standard for ’55 on both the 173-hp two-barrel and 180-hp four-barrel engines.
Another novel feature of the original Pontiac V8 was its Reverse Cooling system. Typical practice on most American V8s is to supply coolant from the water pump first to the cylinder block, next to the cylinder heads. The Pontiac reversed this system (yellow arrow above) by pumping coolant to the cylinder heads first, with brass stampings called gusher tubes that slipped inside the head castings and aimed a coolant stream directly at the exhaust valve regions—ideal for sustained high-load operation. Copied many times in NASCAR and elsewhere, Reverse Cooling was used by Pontiac until 1960, when the division reverted to conventional cooling for reasons that are not entirely clear.
Another unusual Pontiac feature: Unlike most other American V8s, the right bank is offset forward rather than the left. That is, the right-front piston is the first in line on the crankshaft. (However, the left front cylinder is still labeled number one, muddling the issue.) This was done in part, it is said in Pontiac lore, to reverse the gear thrust on the distributor drive.
The Pontiac V8 proved to be one of GM’s more versatile and enduring designs. Offered in numerous sizes—389 and 455 CID are the most familiar—the engine remained in production from 1955 through 1981, powering not only Pontiacs but also some Buicks and Oldsmobiles, and even GMC trucks from 1955 through 1959. For the performance crowd, there were Tri-Power, Super Duty, HO, and Ram Air packages in bountiful variety. Final members of the engine family included a lightweight (lighter than a Chevy, reportedly) 301 CID V8 in 1977, with a turbocharged version for the 1980-1981 Firebird Trans Am, and a 265 CID V8 with a narrow 3.75-inch bore for low emissions. All began right here with the original 1955 Pontiac V8.
Mom had a 59 Bonneville 2dr HT, which I drove occasionally while still in high school. A few months after graduating, my Uncle Jack gave me a 60 Bonneville 2d HT. No doubt about it, the 60 had loads more pep than the 59, though I’ve never really understood why there seemed to be so much difference.
Must have been a problem with your mom’s car. There is only 3hp difference between the 59 and 1960 4bbl Bonneville cars, however the 59 Bonneville compared to a identical equipped 1960 Bonneville is a 100lb. difference. The 59 being lighter by 100lbs equates to at the end of the quarter mile a difference of one tenth of a second. One tenth of a second equates to one car length at the end of the quarter mile.
That was a whole bunch of stuff I didn’t know.
Changing plugs on later ’60s models required moving the air conditioning compressor, on engines so equipped. Replacing distributor caps or setting points (remember those?) on the ’69-’72 Grand Prix was challenging because of the long nose, and rear mounted distributor, despite the convenient “door” in the distributor cap for adjustments. Replacing the fast idle cam on Quadra-jet carbs in a recall campaign was equally “easy”…if one sat atop the engine. Ahhh, such great memories of being a kid working in a Pontiac dealership back then! Thanks for the history lesson on these bullet proof engines, and the memories this post elicited.
From 1959 to early 1980’s A/C equipped cars the procedure for removing the spark plugs on the rt bank cylinder head or 2,4, 6, 8 cylinders is very simple. On the hoist or jack stands, remove the rt front wheel. Every plug is now accessible through the rt. inner fender well opening for the upper control arm, in fact it’s much easier than the easily exposed left side of number 1,3,5,&7
I worked at a Pontiac dealer. To replace the right side spark plugs, I used to put the car up in the air and just let the front wheels hang, then go in over the front tire with a flex socket and a 24-inch extension. Gravy, as we used to say. Usually didn’t have to remove the wheel.
When I worked at Pontiac I used a a flex socket with a 30″ extension. I could finesse the socket to the plug going underneath the compressor.
I think one of the worst thing that happen to Pontiac motors was the nylon coated cam gear. Our parts man would make up 3-4 card board boxes with all the parts to replace the gear and timing chain every morning. By closing they were all gone. In a few cases the nylon covered the oil pump screen and caused major problems.
That nylon coated gear was in nearly if not all every GM’s divisions V-8 engine including Cadillac.
I was always quite impressed with the Pontiac V8. Growing up in a farming community and working for a Pontiac/Buick/GMC dealer the most frequent of these were in GMC trucks which were used well into the 70s. A few of them dropped valves but then, so did the 348 and 409 engines. Also experienced some broken rocker arm studs. I had a 30/4bbl. in my Grand Am. It wasn’t as peppy as my buddy’s Grand Prix with 400 but it still took me where I wanted to go and brought me back. We sold a couple of Firebirds with the 301/2bbl. I thought it was quite unusual to have a 4 bbl sized carb body but only 2 holes were functional. Maybe it saved money in production….
The interesting part about Pontiac engineer Clayton Leach’s ball pivot stamped steel rocker arm ( designed in 1948 ) is that with all new features like Oldsmobile with HydraMatic, Cadillac with variable ratio power steering etc. is each division that designed a new feature was allowed by the corporation a one year exclusivity on the design. So for example Cadillac had to wait for one year before it could use HydraMatic. Chevrolet’s Ed Cole cried to the corporation to make Pontiac give up it’s one year exclusivity for the use of Pontiac’s valve train in the Chevrolet V-8.
Also the Pontiac V-8 was ready to be released for the 1953 Pontiac’s, however Buick cried to the corporation to hold Pontiac back two years because Buick didn’t want Pontiac to steal all the attention from it’s new Nailhead V-8 it was introducing in 1953. It is very plain to see that the Pontiac V-8 was made for 1953 and 1954 Pontiac’s. The frame, suspension and steering are modified for it’s use that never came until 1955.
Pontiac by 1953-54 was known as a old mans car, but it wasn’t Pontiac’s fault for this being so. It was the corporation that always held Pontiac back.
My only Pontiac experience was doing headgaskets on a 63 64 [Australian] 327? Poncho. all fairly simple but everything was heavier than a Chev. And seemed more old fashioned. And all the parts were far more expensive as well. Though some Chev rocker cover gaskets had two sets of holes,, the odd set for Poncho and the even set for Chev. Have not seen them in quite a while though.
And yes like all GM full size cars you had to climb in the engine bay to work on it,,Holdens too were much the same.
While heavy the performance engines always had plenty of grunt, quite a few it seems are being ‘retro fitted’ back to Pontiacs that had been converted to Chev.
Here in South Oz where the US scene is healthy there is quite a few very nice 50s 60s and 70s Pontiacs. Locally assembled Pontis got Chevs in about 66 and a few 69-70 full size Chevs and Pontiacs got 308 Holden V8s as well. Some went to South Africa, and a few to New Zealand as well. And bother where assebled there.
An interesting story would be the late 60s to late 70s Holdens [and Chevs Pontiacs] Fords Chryslers that went CKD to South Africa and NZ that ended up with some odd engines and trans combos. And some odd panel changes as well. Some GM too were assembled and sold here. GMH Statesmans with Chev badges and Chev 6s as well as the 350.
The Falcon GT Superoos ended up in South Africa as Super rhinos on Fairmont GTs
True Pontiac would have been a 326 , Chevy had the 327
Thanks for this very detailed and interesting blog on the Pontiac Motor Division power plant engineering and specs. The Comments are excellent and informative as well , coming from persons who have obviously “been there/done that” in the day. Comment from the Australian gentleman are fascinating. Keep up the good work, Mac.