by Larry Gorden, 2007.  Updated April 2009.

For additional information on the Pontiac V-8 engines see the wikipedia article.

1932 Flat-head V-8. The first V-8 engine that Pontiac offered was in 1932.  It was the same 251-cid 85-hp flat-head V-8 used in Pontiac’s almost-dead parent make, Oakland, during 1930 and 1931.  In 1933 and 1934, Pontiac built only eight-cylinder cars, but they used a straight-eight rather than a V-8.  Pontiac engines up through 1954 were flat-head straight-sixes or straight-eights. Overhead Valve V-8.  The first overhead valve V-8 that Pontiac offered was in 1955.  In these early years of the overhead valve V-8 (1955 through 1960), Pontiac produced only one engine displacement each year.  These engines all used the same basic design with year-to-year increase in bore or stroke, resulting in larger displacement each year from 1955 through 1959.  The 389 cid engine released in 1959 became the Pontiac "bread and butter" engine for GTOs and full size Pontiacs up through 1966.  1981 was the last year that Pontiac built a V-8 engine.

1955 Pontiac Engine

cid = engine cubic inch displacement, in³
Bore & Stroke are in inches.

Main = Main journal size, inches

Rod = Rod Journal size, inches

1955. In 1955, Pontiac introduced a 287 cid V-8 engine, Pontiac’s first production overhead valve V-8.  Engineers Clayton B. Leach and Ed Windeler had developed this cast-iron engine with ball-and-stud rocker arms, gusher-type cooling, pressure-suction crankcase ventilation, and easy-to-cast block construction to keep costs down and make it efficient. It had a very short, stiff crankcase, a lightweight valve train, five main bearings, hydraulic valve lifters, and a Carter WGD or Rochester 2GC two-barrel carburetor. By mid-1955, an optional “power-pack” engine with a four-barrel carburetor was made available but dual exhausts were not available.  This was also the first year of the 12 volt electrical system for Pontiac. Total production for this year was 554,108.

1956.  In 1956, the 287 was bored to 317 cid.  Pontiac really jumped in the horsepower race with built-for-racing NASCAR options carrying dual-quad carburetion and delivering up to 285 hp. This was just the beginning of Pontiac’s entry into the horsepower race.  Only an estimated 200 were produced.  See this link for details on the dual quad engine.  405,730 cars were produced in this year.

1957.  The stroke was increased, and displacement rose to 347 cid.  Larger valves and larger intake/exhaust ports also contributed to performance.  The limited-edition Bonneville (630 units produced, all convertibles) got a 315-hp fuel-injected version of this engine.  There was also a 290-hp “Tn-Power” (three two-barrel carburetor) option, plus a 317-hp NASCAR tri-Power engine.  The tri-power became a relatively popular Pontiac option for many years (through 1966).

1958.  The engine was bored again to produce a 370 cid engine.  Fuel injection was made an option and again there were Tn-Power and NASCAR (a.k.a. Tempest 395-A) options delivering horsepower numbers as high as 330.

1959.  In 1959, the 370 was stroked out to become the famous 389 cid Pontiac V-8 produced up through 1966. Fuel injection was gone, but the highest output level was now up to 345 hp, thanks to a Tempest 420-A option with 10.5:1 compression and Tri-Power carburetion.  See 1959 Engine Identification Chart  (a page in Master Parts Catalog) for a complete list of engines.

1960.  The 389-cid V-8 was used in all Pontiacs in 1960.  Performance wise, the 1960 engine was the similar to the 1959 engine, the high output (425-A option) was bumped up slightly in horsepower to 348 HP.  A significant change was made in how water was circulated though the engine.  Pervious Pontiac engines circulated water though the heads first, then into and through the block.  This was called “reverse flow” and was a selling point for Pontiac engines.  In 1960, the water flow was changed to enter the engine block first and then into the heads.  See Pontiac Engine Cooling for more information.  See 1960 Engine Identification Chart (a page in Master Parts Catalog) for a complete list of engines.

1961.  In 1961, the new compact Tempest offered a different type of V-8. This was a 215-cid 155-hp job built by Buick. Also showing up very late in the calendar year was a 421-cid V-8.  In this year, Pontiac began casting the engine block with thinner walls producing a lighter engine.  Water ports from the heads to the intake manifold was changed slightly, making the 61 and later intake manifolds incompatible with previous engines.  A four cylinder was offered in the new Tempest beginning this year.  This engine was essentially half of the 389 V-8 engine.

1962.  The 421 engine became a regular production option in 1962.  It produced 405 hp. The 421 did not differ greatly in basic design from the 389-cid V-8, but featured lighter connecting rods and much larger crankshaft journals. The 421-cid, 405- hp designation became well known after it appeared on the hoods of many NASCAR stock cars and Super-Duty drag cars.

1963.  Derived from the 389 was a new 326-cid V-8 that arrived in the 1963 Tempest. It was a small-bore version of the bigger engine with a four-barrel carburetor and 260 hp. The 1963 326 engines used a 3.78-inch bore size for an actual 336 cubic inch displacement (same bore/stroke/displacement as the 1959 GMC engine, also a small bore version of the Pontiac 389-cid engine).  In 1964 Pontiac reduced the bore size to what was correct for 326 inches of displacement, a 3.719-inch bore.  Pontiac continued with Tri-Power options for both the 389 and the 421. Two 421 HO. V-8s produced 353 and 370 hp, respectively, but the hottest options of all were the 390-, 405-, and 410- hp 421 Super-Duty choices. These featured up to 13.0:1 compression and came with a single four- barrel, three two-barrel, or dual four-barrel carburetors. They were intended strictly for racing and to make Pontiac the competition king.

1964.  In 1964, GM management banned corporate racing involvement and Pontiac was forced to dump the Super-Duty program. The 421 HO, options were allowed to remain, and 370 hp was tops. The 389 was still around, and the Tempest retained the 326 until the GTO arrived at midyear. The first true “muscle car,” this so-called “Goat,” came with a base 389-cid 325-hp V-8, plus an optional Tri-Power version of the same engine with 348 hp. Pontiac’s intention was to use the GTO to maintain its high-performance image after the racing ban. A good job was done of this.

1965, 1966.   By 1965, the Tri-Power GTO was up to 360 hp.  1966 was the last year of production for the 389 cid engine and tri-power carburetors.

1967.  The 400-cid V-8 that introduced in 1967 Pontiacs was a bored-out version of the 389, and a new 428 was a bored-out 421. The extra cubes were added to mask the fact that Tri-Power options were no longer offered. The top 400-cid V-8 was a four-barrel version for the GTO that had the same 360-hp rating as the previous 389 Tn-Power option. Likewise, the top 428-cid engine carried the same 376-hp rating as last year’s 421 Tri-Power job. The new Firebird used the 326 as its base V-8 and offered 400 and 400 Ram Air options.

1968.  For 1968, Pontiac released a new 350 cid engine for the Tempest and Firebird. It was created by boring the 326.

Never seeing the light of day was Pontiac’s only really new 1969 engine, a 303-cid small-block V-8 that never got too far beyond the prototype stage. It was developed to make the Firebird competitive in Sports Car Club of America Trans Am racing, but only about 25 racing cars were fitted with these short-stroke, tunnel-port V-8s.  

1970.  A bored-and-stroked version of the big-block Pontiac V-8 arrived in 1970. This 455-cid engine was not really one of the year’s high-performance options, but it had huge amounts of torque and potential for future development.  Another engine not seeing the light of day was the 1970 366-cid engine.  In talking about the 1969 303-cid and 1970 366-cid engines, Wallace Racing (www.WallaceRacing.com) says "Although both these engines were developed by the factory, they were never put into production . Complete 303 or 366 assemblies are available from aftermarket sources if the price does not bother you."

1971.  Additional high-performance options were offered in 1971 including the Trans Am with a 335-hp 455-cid Ram Air version (also optional in the LeMans/GTO).

1972. When a Nova-based compact car revived the Ventura nameplate in 1972, a Chevy-built 307-cid V-8 was under its hood. Otherwise. Pontiac stuck with the 350-, 400- and 455-cid V-8s with up to 300 net horsepower (a new rating system).

1973.  In 1973, the Ventura got the Pontiac 350 instead of the Chevy 307; in 1975 it got an Olds-built 260. By that time, Pontiac V-8s had catalytic converters and other power-robbing economy and emission changes.

1976.  The last year for the big 455 was 1976.

1977.  In 1977 a 301-cid engine was the base V-8 in many models, while the Ventura used a 305-cid V-8 made by Chevrolet or GM of Canada. There was also an Oldsmobile 403-cid “alternate” V-8 for Pontiacs sold in California.

It was the 301-, 305-, 350-, 400-, and 403-cid V-8s for the next several years. 

1980.  In 1980, all engines over the 350 were dropped, and a new 265-cid V-8 was optional in Firebird. LeMans, Grand Prix, Catalina, and Bonneville models. This 4.3-liter V-8 was built by Pontiac and also supplied to Oldsmobile. Also new in 1980 was a 350-cid Olds-built diesel.

1981. was the last year Pontiac built a V-8 engine.  Future Pontiacs would use primarily the generic General Motors engines.

Article from 1981 Car Exchange