All 455 Olds Rocket Engines Horsepower Specs

by James Jordan
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All GM car makers had a 455 engine, and each car under that umbrella had its own version. Oldsmobile's version was part of the Rocket series of V-8 engines that powered its cars.


The Olds 455 engine was created out of the 425 engine in 1968 by changing the internal workings. The bore was kept the same and the stroke was extended. The engine was used across the Oldsmobile lineup through 1976 and horsepower ranged from 275 up to 400.


The bore and stroke (the size of cylinder and the distance it moves) was 4.126 and 4.25 inches through most of the life of the engine. With a longer stroke, torque was generally high. In the 1968 Delta 88 it had 490 ft.-lbs. of torque, or pulling power. Two- or four-barrel carburetors affected horsepower, as did the compression ratio, which varied from 8:1 to 9.5:1. The compression ratio is how much the fuel and air mixture is compressed at combustion.

Power Ratings

The 1968 Delta 88 produced 310 horsepower with the 455 engine, while the Ninety Eight with a four-barrel produced 365 horsepower. In the early '70s the fuel crisis and rising emission standards ended the muscle car era. By 1975 the horsepower in the Ninety Eight was down to 190.

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