1978 Chevrolet 454 Specifications

by Moss Strohem

General Motors (GM) produced the 454 engine from 1970 until 2001. GM initially used the 454 big-block Chevy (BBC) in Chevrolet's high-performance and full-size passenger cars and then added it as an engine option in 1973 and later Chevrolet and GMC trucks. GM developed variations of the BBC known as Mark IV, Gen V and Gen VI. The 1978 454, a member of the Mark IV BBC series of engines, was not available in passenger cars.

Engine Block Design

Original designed in the early 1960s, all big block Chevy engines were based on an eight-cylinder, 90-degree V configuration. With the exception of the aluminum ZL-1 engine, engine blocks were made of cast iron and used steel cylinder bore sleeves. Chevy produced the 1978 454 blocks with both two- and four-bolt main caps. Displacement occurred via a 4-inch crankshaft stroke and a 4.25-inch-diameter cylinder bore. The cylinder banks centered the bores on a 4.84-inch spacing. Crankshafts incorporated either cast iron or forged steel, with five main bearing journals. Due to the long crankshaft stroke, GM engineers fitted externally balanced harmonic balancers and flywheels to the engines. The connecting rods were made of forged steel, and the pistons were low-compression cast-aluminum designs. The camshaft housing was located in the block along a centerline directly above the crankshaft.

Cylinder Heads, Intake and Cam

Unlike its earlier high-performance 454 engines, Chevy designed the 1978 engine for truck applications with a goal of low-performance, high-torque output. Earlier high-performance engines used heads with rectangular intake ports with large intake volumes and valve diameters. The truck 454 used smaller oval port-shaped intake ports with small valves which promoted low revolution-per-minute (rpm) power and torque rather than "all-out" high rpm horsepower. The camshaft was a hydraulic flat-tappet, low-lift, short-duration design that improved torque output at a lower-rpm range than performance grinds. The induction system consisted of a cast-iron low-rise intake manifold and a spread-bore Rochester Quadrajet four-barrel carburetor.

Power Output

The mid to late 1970s saw some of the lowest-rated engines in history due to tightening emissions requirements and lower compression ratios. The 454 engine produced about 230 horsepower and 360 foot-lbs. of torque.

Performance Enhancements

Many of these low-performance engines allow for upgrades and modifications for performance applications with aftermarket parts. With careful selection of components, many car enthusiasts have built 454s that produce power outputs approaching 600 horsepower or more.

About the Author

Moss Strohem has a background in business and finance, and an avid interest in youth sports, health, nutrition and physiology. He writes both technical information and market commentary as a private consultant and has researched and authored business plans.

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