List of GM bellhousing patterns

Though General Motors has manufactured many different engines, it has kept variance in the bell housing patterns to a relative minimum.

Nearly identical to the GM small corporate/metric pattern, except that the starter is located between the cylinder banks, and the lower right bolt hole is moved outward by roughly one inch.

Atlas family engines use a unique bellhousing pattern which no other GM motors share.

Some transmissions, most notably the TH200-4R, take advantage of this by integrating both specifications into a "universal" bolt pattern casting.

The completely re-engineered Generation III Ecotec includes a new uniquely shaped bellhousing pattern.