This adapter mounts a spin-on cartridge oil filter on all 1968-2000 Gen 1 small block chevy engines and all 1968-1990 Mark IV big block engines. Not for use with 1988-2000 4x4 trucks (that used a right angle adapter) or vehicles that use an oil cooler. This adapter does not require a gasket, it mounts directly to the engine block. It contains a filter bypass valve. Requires two attaching bolts P/N 3951644.