List of GM bellhousing patterns

The following is a 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.

Chevrolet V8 pattern

So named because it began with Chevrolet's V8 engines.

Chevrolet big-block V8's
Chevrolet small-block V8's
GM Vortec 4300 90° V6
GM Iron Duke RWD inline 4 (Early RWD Variants, later versions may use a FWD pattern, and have two possible starter locations)
Jeep 2.5L/151 in³ Jeep used the GM Iron Duke inline 4 1980-1983. These use a Chrysler Torqueflite 904 automatic transmission with a Chevrolet bellhousing.
Chevrolet Inline 6 (1963 on)
Chevrolet 153 Inline 4 (Chevy II, pre-Iron-Duke)

GM metric pattern

Also called the GM small corporate pattern

This pattern has a distinctive odd-sided hexagonal shape.

GM 60° V6 family FWD/RWD V6; 2.8/3.1/3.4 L
Buick FWD/RWD 90° 3800 V6
Cadillac 4.1/4.5/4.9 L V8
Isuzu 3.5L DOHC V6
1984-03 Jeep/AMC/Chrysler 2.5L/150 in³ I4 found in Jeep Cherokee, Wagoneer, Comanche, and Wrangler models (except Grand Wagoneer & Grand Cherokee) and 1996-2002 Dodge Dakotas.
Jeep/AMC 2.8L V6 (GM engine)
GM Iron Duke FWD inline 4
1984-93 GM Iron Duke/Tech-4 RWD inline 4

Northstar pattern

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. Being nearly identical, it too has the distinctive odd-sided hexagonal shape.

All Cadillac Northstar V8's
Oldsmobile Aurora L47 V8
Oldsmobile Intrigue LX5 V6

Pre 1965 Buick and Rover V-8 Round pattern

Buick/Oldsmobile/Pontiac 215 Aluminum V-8
1967 through 2004 Rover V-8 based on the GM 215

Buick, Oldsmobile, Pontiac (BOP) V8 pattern

Post-1965 Buick/Oldsmobile/Pontiac RWD V8's
Buick pre-3800 90° RWD V6's
Jeep "Dauntless" 225 in³ oddfire V6 (1967-1974)
Cadillac cast iron V8s after 1967 (1968-85 472 and 500, 368 and 425)
Starters are on the left side on Olds and Pontiac and the right on Cadillac and Buicks.

Cadillac V8 pattern, pre-1967

Early Cadillacs manufactured before 1965 used a "round top" bellhousing much similar to early Buicks; around 1965, the bellhousing pattern was revised until the BOP bolt pattern was adopted in 1968.

GM 4-cylinder pattern

GM Quad-4 family

GM Ecotec 4-cylinder pattern

GM Ecotec Family II

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