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Pontiac 421 V8 Engine

In 1961 Pontiac continued to push the horsepower upwards with the release of the 421 engine. As with all other Pontiac V8 motors that evolved from the 316 V8, the 421 was simply a bored out and stroked version of the popular Pontiac 389 V8. What was most interesting about the 421 engine in the beginning was that it was a dealer installed option only known as the SD (Super Duty) 421. These motors were built mainly for NASCAR or other racing purposes and were equipped with all the extra racing goodies that people were looking for. A Pontiac SD 421 came with forged steel rods and crankshafts for extra durability. In 1961 and 1962 they were available with either one 4 barrel carburetor or a dual 4 barrel carburetor setup depending on whether the buyer wanted to head to the racetrack or drag strip.

By 1963 Pontiac decided it was time to release the 421 V8 officially to the general public and the motor would continue to be available until the end of the 1966 model year. The 421 SD Tri-Power engine offered during these years produced the highest horsepower of any motor in the Pontiac V8 lineup at 376 bhp. There were a few 1962 Grand Prix models that came with a 421 SD from the factory so if someone is lucky enough to have one today then they have a car that is probably worth some decent money simply because of the rarity of these models.

 

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Engine Specifications

1961 - 1963 with 4 Barrel Carb
SD (Super Duty)

Max Brake Horsepower - 353 @ 5000 rpm
Max Torque - 455 @ 3400 rpm
Stroke - 4.0
Bore - 4.09375
Compression - 10.75
Firing Order - 18436572

1961 - 1964 with 3 X 2 Barrel Carbs
(Super Duty with Tri-Power Setup)

Max Brake Horsepower - 370 @ 5200 rpm
Max Torque - 460 @ 3800 rpm
Stroke - 4.0
Bore - 4.09375
Compression - 10.75
Firing Order - 18436572

1964 with 4 Barrel Carb
Max Brake Horsepower - 320 @ 4400 rpm
Max Torque - 455 @ 2800 rpm
Stroke - 4.0
Bore - 4.09375
Compression - 10.75
Firing Order - 18436572

1964 with 3 X 2 Barrel Carbs
(Tri Power Setup)

Max Brake Horsepower - 350 @ 4600 rpm
Max Torque - 454 @ 3200 rpm
Stroke - 4.0
Bore - 4.09375
Compression - 10.75
Firing Order - 18436572

1965 - 1966 with 4 Barrel Carb
Max Brake Horsepower - 338 @ 4600 rpm
Max Torque - 459 @ 2800 rpm
Stroke - 4.0
Bore - 4.09375
Compression - 10.75
Firing Order - 18436572

1965 - 1966 with 3 X 2 Barrel Carbs
(Tri-Power Setup)

Max Brake Horsepower - 356 @ 4800 rpm
Max Torque - 459 @ 3200 rpm
Stroke - 4.0
Bore - 4.09375
Compression - 10.75
Firing Order - 18436572

1965 - 1966 with 3 X 2 Barrel Carbs
(Super Duty with Tri-Power Setup)

Max Brake Horsepower - 376 @ 5000 rpm
Max Torque - 461 @ 3600 rpm
Stroke - 4.0
Bore - 4.09375
Compression - 10.75
Firing Order - 18436572