I'm working on a Firebird for my daily driver and I was wondering what engines would fit a tranny? It currently has a Oldsmobile 403 (father in law says its a big block) that needs a rebuild. It has a new tranny with a shift kit so I don't like the idea of switching the tranny out. I however, would like to get more than 6 mpg and would be rebuilding the 403 later once I can afford another car.
403 Firebird engine swap
Sep 05, 2007
1 Replies
Your father-in-law is wrong - it's a small block (basically an Olds 350 with big pistons), but it doesn't really matter. The transmission has the Buick-Olds-Pontiac-Cadillac bellhousing pattern. There are a wide variety of engines that will fit that. It was standardized around 1960. Any B-O-P-C engine used in a rear drive car after 1960 will fit the tranmission, except for the Buick V-6's built after about 1988 or so and used in Firebirds (which are rear drive, of course). I don't think any other rear-drive BOPC engines were actually built anyway after the mid - 80's. I guess the Olds 307 was the last of the BOPC V-8's.
As you can probably guess, any small-block Olds V8 will bolt right in, and any Pontiac V-8 is fairly easy to put in because there are so many Pontiac-powered Firebirds to rob parts from.
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