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Pontiac 455 V8 Engine

The 455 Pontiac V8 was introduced in 1970 and provided large-bodied Pontiacs a torque-friendly engine. Prominently featured in the Pontiac Bonneville, the 455 was also used in the GTO, Trans Am, and the Firebird.

The 455 was an improvement on the Pontiac 428 V8. High Output and Super Duty versions of the 455 were added in succeeding years. The Pontiac Grand Ville series also featured the 455 beginning in 1972.

Although the 455 has great torque, the 455’s horsepower was often adjusted due to various emissions changes, advertising gimmicks, or to appease insurance companies. The 455 High Output engine had improved cylinder heads as well as better intake and exhaust ports while the Super Duty, made in 1973, was able to produce 290 horsepower in spite of more strict emissions standards. The 455 was discontinued after 1976.

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I just bought a base 1972 Pontiac Bonneville with the V code 185hp single exhaust 455 motor and want to upgrade it the the YA, YB or YC 4bbl dual exhaust motor of 220hp or 250hp - what are the specific part differences between the base V code motor and these higher horse power motors - carb, intake, cam, exhaust, etc.. Do not want to change the heads or pistons = expensive.

Thanks for any help
Mike
#1 - Mike Baker - 11/27/2011 - 12:53
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Engine Specifications

1970 - 1971 with 4 Barrel Carb
Max Brake Horsepower - 325 @ 4400 rpm
Max Torque – 455 @ 3200 rpm
Stroke – 4.21
Bore – 4.15
Compression – 8.2
Firing Order - 18436572

1971 High Output (H.O.)
Max Brake Horsepower - 335 @ 4800 rpm
Max Torque – 480 @ 3600 rpm
Stroke – 4.21
Bore – 4.15
Compression – 8.2
Firing Order - 18436572

1972 with 4 Barrel Carb
Max Brake Horsepower - 300 @ 4000 rpm
Max Torque – 415 @ 3200 rpm
Stroke – 4.21
Bore – 4.15
Compression – 8.2
Firing Order - 18436572

1973 - 1974 with 4 Barrel Carb
Max Brake Horsepower - 250 @ 4000 rpm
Max Torque – 370 @ 2800 rpm
Stroke – 4.21
Bore – 4.15
Compression – 8.2
Firing Order - 18436572

1973 - 1974 Super Duty
Max Brake Horsepower - 290 @ 3600 rpm
Max Torque – 380 @ 3600 rpm
Stroke – 4.21
Bore – 4.15
Compression – 8.2
Firing Order - 18436572

1975 with 4 Barrel Carb
Max Brake Horsepower - 200 @ 3800 rpm
Max Torque – 330 @ 2000 rpm
Stroke – 4.21
Bore – 4.15
Compression – 8.2
Firing Order - 18436572

1976 with 4 Barrel Carb (H.O.)
Max Brake Horsepower - 200 @ 3800 rpm
Max Torque – 330 @ 2000 rpm
Stroke – 4.21
Bore – 4.15
Compression – 8.2
Firing Order - 18436572