Pontiac V8 Engine – The engine that sparked the Muscle Car Era

Pontiac V8 Engine and Logo

Pontiac V8 Engine and Logo

The Pontiac V8 Engine

The Pontiac V8 engine was designed in the late 40s, and came equipped with overhead valves and a new innovative, lightweight valve train. This engine proved so reliable that production lasted from 1955 to 1981. Within the 26 years of production, Pontiac continued to develop and improve on the design. The engines were produced in many configurations starting from 287 cubic inches (4.7 L) all the way up to 455 cubic inches (7.46 l). Amazingly, achieved by using the same block outer dimensions and configuration.


Pontiac V8 Engine Codes and Specifications

Pontiac V8 Engine Tune-Up and Torque Specifications

Pontiac V8 Head Casting numbers and Specs

Pontiac V8 Intake Manifold 


A Brief History of the Pontiac V8 Engine.

In 1946 Pontiac began developing a 269 cubic inch (4.41 L) L Head (flat head) V8.  Unfortunately compared to the Oldsmobile’s new overhead valve 303 cubic inches (4.97 L) V8 it was extremely underpowered. They continued using their inline 8-cylinder engine. However, they slowly worked on the development of a new 287 cubic inch (4.7 L) Overhead valve V8.

Management changed in 1952 and the development of the new Pontiac V8 engine accelerated. Plans were to produce models with the new v8 by 1953. The delayed start to the V8 gave the Pontiac engineers an edge by learning from the mistakes made on Oldsmobile, Buick, and Cadillac V8’s.

However, production delayed until 1955. Oldsmobile and Buick protest to GM management because the engine was so superior it would hurt their sales.


Pontiac Engine Bay

Pontiac Engine

The Pontiac V8 Engine debuted in 1955 and featured the following:

  • “Gusher cooling system” (reverse-flow coolant circulation).
  • Pressure-suction crankcase ventilation.
  • Easy-to-cast block construction to keep costs.
  • It had a noticeably short, stiff crankcase.
  • A lightweight valve train.
  • Five main bearings.
  • Hydraulic valve lifters.
  • Stamped rocker-arm system.


“New innovations gave the new Pontiac V8 engine more power while reducing Cost.”

The new “gusher cooling System” helped keep the engine at a more optimal operating temperature. All new stamped rocker arms that mounted to a ball pivots with studs set into the head. This set up did not need a separate shaft to hold the rockers. The revolutionary new lightweight drive train gave more consistent valve operation and was also cheaper to produce. Chevy quickly adapted it for their new V8.  Chevrolet management had convinced GM to allow them to also fit the system to their engine for the 1955 model year.


Evolution of the Pontiac V8 Engine.

1955 to 1957 – The 287, 317, 340 and 370

The Pontiac V8 engine evolved yearly, starting with the” 287 Strato Streak” in 1955.
A 287 cubic inches (4.7 l) displacement with a 3.75” bore and 3.25” stroke and a compression ratio of 8.00:1. The all-new 287 producing as much as 200 Horsepower.

In 1956 the displacement increased to 316.6 cubic inches (5.19 l) by increasing the bore to 3.9375″. The 317 with a 4 barrel carburetor was rates as high as 285 HP @ 4800 rpm.

Displacement increased by 30 cubic inches (0.49 l) in 1957. The stroke increased to 3.5625” giving a total displacement of 347 cubic inches (5.69 l).  For the first time, the famed “Tripower” (Three 2 barrel) carburetor set up was a new option.

Also, for 1957, the Bonneville came standard with a 347 equipped with a Rochester Fuel Injection system. Top configuration of the 347 engine producing 300 HP @ 4800 rpm.

For 1958 the Pontiac V8 engine size increased to 370 (369.4 cubic inches) with a 4.1666” bore and a 3.562” stroke. Fuel injection became an option on all models that year. However, due to the $500 price tag, Pontiac only produced 400 models with Fuel Injection. The top 370 producing 310 HP @ 4800 rpm.


In 1959 engine size increased to 389 cubic inches (6.37 l) with a 4.166” bore and 3.75 stroke. This was the beginning of the famed powerhouse Pontiac 389. The 389 produced 215 to 368 HP depending on the configuration. In 1964 Pontiac installed the 389 in their lighter mid-size Tempest GTO, starting the “Muscle Car” era. The 389 was the standard engine on the GTO up to 1966.

From 1959 to 1966 Pontiac continues making improvements. They also began offering many specialty performance parts for the engines like windage trays and 4 bolt main bearings. The 389 was such a winner on the race track that it was nicked named “trophy V8”. The horsepower of the 389 ranged from 200 to 370.


A dealer option for 1961 the “421 Super Duty” came with larger main journals, and lighter Connecting Rods. With a 4.09” bore and a 4” Stroke it increased the displacement to 421.19 Cubic Inches producing 405 HP. The Super Duty was developed for use in NASCAR, Stock Car, and Drag Racing. Stating in 1962 the “421” and the “421 SD” engine became available as a factory option until 1966.  The 421 SD produced up to 410 HP.


In 1963 Pontiac needed a smaller displacement engine for their intermediate and mid-size models. They reduced the bore of the “389” to 3.72” to get a displacement of 326 cubic inches (5.34 l). The 326 replaced the Buick 215 V8 offered in previous years.


For 1967 once again Pontiac increased the displacement of the engines. The 389’s bore increased to 4.12″, given a displacement of 400 cubic inches (6.55 liters). The 421 was bumped up to 428 cubic inches. And, in 1968 the 326 was also increased to 350.

Also, for 68 the heads were redesigned with new combustion chambers and improved valve angle for better performance and reduce emissions.


Pontiac Grand Prix - Engine

Pontiac Grand Prix Engine


All 400 have a 4.12” bore and a 3.75” stroke. For 1967 the valve angle changed from 17 to 14 degrees, However, they still used the closed combustion chamber. In 1968 heads were manufactured with open chambers, and they also got the 14-degree valve angle.

In the late 60s as the muscle car war heated up, the 400 got many specialty performance upgrades.  These engines power output ranged from 250 HP to 370 HP. However, low-end torque rated at 445 lbs. Ft. @3000rpm is what gave these engines their incredible drivability and performance.


400 Ram Air

Introduced in 1967 and was the top engine option for the Firebirds and GTOs rated at 360 HP. It had a higher duration Cam, and Cast-iron headers. Also, D port heads with a closed combustion chamber and taller valves at a new 14-degree angle.

400 Ram Air II

The Ram Air II was a 366 HP power 400 engine produced in 1968. The engine used Round Port heads and Cam with 308/320-degree duration with 0.47-inch lift.

1969-70 Ram Air III

The RAM Air III engines were an option on the 1969 and 1970 Firebird and GTOs. They were also the Standard Engine on the Judge” and also the “Trans Am”. The engine used Heads D port heads, 288/302 duration camshaft, cast-iron headers, and an outside air induction system. The Ram Air III engine was rated at 366 bhp.

1970 Pontiac GTO Judge Ram Air IV Convertible - Engine

1970 Pontiac GTO Judge Ram Air IV Convertible Engine

Ram Air IV

In 1969 and 1970 the Ram Air IV engine was the top option for the Firebirds and GTOs. The engine used Round Port heads like the Ram Air II, but had taller intake ports. The block was 4 bolt mains, aluminum intake-manifold, and cast-iron headers.

Ram Air V

The Ram Air V engines were pure race engines that could be ordered by Pontiac Dealers. It used tunnel-port heads with incredibly large intake and exhaust ports. The intake ports are so large that the pushrods run through the center of the port.
Pontiac produced 4 versions of the Ram Air V engines. A 303 cubic inch (4.97 l) to use for Trans-Am racing. A 366 cubic inch for NASCAR, A 400 cubic inch, and 428 cubic inches for drag racing.
A dealer-installed option the Ram Air V engines are very rare.


The new 428 had a 4.12” bore and a 3.25” stroke with a total cubic inch of 426.61. High output versions of the 428 engines came in at 390 HP. The 428 was only available in Pontiac full-size cars. Nevertheless, dealers like Royal installed the 428 in GTOs and Firebirds.


For 1968 the 326 was also bumped up to 350 cubic inches (5.74 l). A 3.875” Bore and 3.75 Stroke total displacement of 353.8 cubic inches (5.8 l). Available in 2 barrels, 4 barrels, and an HO option available for the Tempest and Firebird.


A 303 cubic inch (4.97 l) was developed for Tran Am Racing in 1969.  However, the 303 was not available in any production cars. The engine had a 4.121” bore and 2.84” stroke. The 303.63 cubic inch (4.98 l) motor produced 475 HP.

1970 -1981

In the 70s further emissions requirements from the EPA and the gas crisis in 1973 forced the isolation of horsepower robbing emission control devices. The heyday of high output big muscle engines was over. However, Pontiac engineers found ways of producing some outstanding engines.

350 and 400

Production of the 350 and 400 continued in the same bore and stroke configurations up to 1979.


The 455 was Introduced in 1970 and replaced the 428. The engine had a 4.152” bore and a 4.21” stroke. It had a total displacement of 456.12 cubic inches (7.47 l). GM restricted all engines above 400 cubic inches to full-size cars. However, the restriction was removed and so Pontiac was able to offer the 455 as an option for GTO and the Firebird.

A key feature of the Pontiac 455 V8 was the outer dimensions were the same as the smaller 350 and 400 blocks. Pontiac did not adapt a small block big-block configuration like other GM divisions. This was an advantage because they did not have a size issue to contend with installing on the smaller models.

455 HO

The 455’s horsepower ratings were lower than the previous year’s 400. However, the engines increased Torque more than made up for the Horsepower deficit. In 1970 the 455 HO with round port heads was rated at 370 HP @ 4600 rpm and 500lb-ft @3100 rpm.

For 1971 further smog restrictions continued to diminish the 455’s output. The 455 HO power decreased to 335 HP @ 4800 rpm and 480lb-ft @3600 rpm.

The 455 Super Duty

In 1973 and 1974 Pontiac produced the “455 SD” (Super Duty). The 455 SD featured a reinforced block, forged connecting rods, improved round port cylinder heads, and a special oiling system. A detuned engine developed by Pontiac for NASCAR.  The engine power output came in at only 310 HP. However, the reading obtained using the new SAE net horsepower rating system. And, further detuned to 290 HP in mid-1973 to pass the new EPA emissions test.

Production of the 455 stopped in 1976.


In 1977 Pontiac introduced the 301 which was the last Pontiac V8 configuration. This engine had a 4” bore with a 3” stroke giving a total displacement of 301.6 cubic inches (4.94 l).  In 1980 a Turbo version of the 301 was used in the Trans Am. The Engine produced 210 HP @ 4400 rpm and 345 lb-ft @ 2800 rpm.  Production of the 301 stopped in 1981 and was the last V8 produced by Pontiac.

The Pontiac V8 engine remains one of the catalysts that started the muscle car era of the 60s. It proved to be efficient, reliable while provided incredible power and torque. The Pontiac engine did not make the most horsepower it wasn’t the lightest and it did not have Hemi heads. However, this engine propelled some of the most exciting muscle cars in history.


One Response to “Pontiac V8 Engine – The engine that sparked the Muscle Car Era

  • Charlie Rich
    3 years ago

    Excellent article! I’ve been a Pontiac lover my whole life as it was my Dad’s favorite also. From a 52 Star Chief to a 61 Catalina, a 66 GTO to my most beloved 69 Grand Prix, I’m blessed to say I’ve lived the Pontiac dream!

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