Chevrolet 400 Engine Specs

The Chevrolet 400 is a naturally aspirated OHV V8 petrol engine produced from 1970 to 1980, developed as the largest-displacement member of the small-block Chevrolet family by combining an unusually large bore with a longer stroke crankshaft borrowed conceptually from Chevrolet's big-block engines. It was used primarily in mid-size and full-size Chevrolets including the Chevelle, Impala, Monte Carlo, Caprice, and El Camino, generally as a torque-focused option for buyers wanting strong low-end pulling power rather than high-RPM performance.

Producing 150-265hp and 406-563Nm of torque from 6,570cc, the 400 uses the familiar small-block OHV 16-valve architecture but with siamese cylinder bores (where adjacent cylinder walls touch, without a water jacket between them) to accommodate its larger bore within the standard small-block deck height - a design compromise that improved displacement but concentrated more heat in the cylinder walls between adjacent bores than in other small-block variants.

That siamese-bore design is the most important thing for any prospective buyer or owner to understand: the reduced cooling capacity between adjacent cylinders makes the 400 somewhat more prone to cylinder wall and piston ring wear over time compared with other small-block displacements, particularly if the cooling system isn't kept in excellent condition or if the engine has been run hot at any point in its history. Because of this characteristic, the 400 is generally considered less desirable for high-RPM performance use than the 327 or 350, and it built its reputation instead as a smooth, torquey engine well suited to heavier mid-size and full-size cars, especially those originally intended for relaxed highway cruising rather than spirited driving. As with any small-block variant of this era, timing chain wear, general seal and gasket deterioration appropriate to the engine's age, and careful attention to cooling system health should all be part of any pre-purchase evaluation, and parts availability remains good thanks to the broader small-block Chevrolet aftermarket, even though the 400-specific block casting is less commonly used as a basis for performance builds than the smaller-bore variants.