Q: Paul, can you tell me, please, what the difference would be between the Lycoming O-320-E2-D and the O-320-E2-G?
A: Dave, there really isn’t much of a difference between the Lycoming O-320-E2D and the O-320-E2G.
According to the Lycoming Certificated Engine listing (SSP-110-1), the O-320-E2G is the same as the O-320-E2D except the O-320-E2G uses the oil sump and intake pipes from an O-320-A series engine.
Since you didn’t identify whether you are dealing with a Narrow Deck or Wide Deck engine configuration, I’d recommend that you refer to the following Parts Catalogs just to make sure there is no confusion regarding the correct part numbers used in each application. The Parts Catalog for the Narrow Deck engines is PC-103, and for the Wide Deck engines you should refer to PC-203-6 for the E2D series and PC-203-7 for the E2G series engine.
I believe this information should provide you with the proper information to resolve any questions you may have regarding the difference between these two models.