GM Bellhousing Bolt Patterns

The General Motors corporation was responsible for producing seven common bellhousing patterns. Allot of engine types shared bolt patterns but several were also exclusive to their own engine family. Below you will find information on which engine uses which bellhousing bolt pattern. You may ask yourself "why do I care about this information?" Well as any true hot roder will know, engine swaps are one of the best ways to make your vehicle the best one of the bunch. But in these cases you may not be so inclined to swap out a perfectly good transmission and drivetrain. So with the information below you can choose any engine that will bolt to your transmission or even figure out which vehicle and engine combination to look for when shopping for a transmission in a junkyard.

Bellhousing	Engines
Chevrolet bolt pattern.	Used on all Chevrolet V8's to this date. Also used on Chevrolet 90degree V6's Small Block Chevy, Big Block Chevy,  3.8L (229ci) V6 (not to be confused with Buick 3.8L), 4.3L V6
Buick, Olds, Pontiac, Cadillac (BOP) bolt pattern	Used on all Buick, Olds, Pontiac and Cadillac's until the cars switched to Chevrolet engines. Buick, Olds, Pontiac and Cadillac V8's, 4.1L (255ci) V6, 3.8L(231ci) V6,
GM Small Corporate Pattern	Used on Chevy 60 degree V6's, 4 cylinders and other FWD engines 2.0L (OHV I4), 2.2L (OHV I4), 2.5L (OHV "Iron Duke" I4), 2.8L (60* V6), 3.0L (90* V6), 3.1L & 3100 (60* V6), 3.3L & 3300 (90* V6), 3.4 & 3400 (60* V6), 3500 (60* V6), 3.6L (60* V6), 3800 (90*V6), 3.9L (60* V6), 4.1L V8, 4.5L V8, 4.9L V8
GM Ecotec 4 Cylinder	A late 90's GM 4 Cylinder used across several FWD car lines. An all aluminum engine featuring impressive technology and modern design. 2.0L, 2.2L, 2.4L
GM 4 Cylinder Pattern	Unique to a select line of GM 4 cylinder front wheel drive engines. 2.3L (SOHC I4), 2.3L ("Quad Four" DOHC I4), 2.4L ("Twin Cam" DOHC I4)
Cadillac Northstar Pattern	A breed of Cadillac V8's that feature dual overhead cams. Some versions feature variable valve timing as well. 4.0L (Oldsmobile engine built by Cadillac and based on Northstar), 4.6L V8
Isuzu 4 Cylinder	Used in cars and trucks such as the Chevrolet Nova and the Chevrolet S-10. This 4 cylinder from Japan found its way into a few GM vehicles. 1.6L, 1.8L, 1.9L, 2.0L