86 firebird engine swap from v6 to 73 sbc 400 and th350

Asked by GuruR2R23 Feb 15, 2020 at 12:41 AM about the 1986 Pontiac Firebird

Question type: Car Customization

thinking of buying 86 firebird and want to put my 73 400 sbc and th 350 in it. I
will scrap the computer. The motor and trans are currently in an 82 grand prix
and wondered what, if anything, will interchange, and what I should replace or
modify to fit this drive train.

5 Answers


This sounds like a question for a Pontiac performance forum, where they can go into specifics (hard to do that here). As to fitment, people swap in big blocks into 2nd and 3rd gen Firebirds all the time, so more than doable. Obviously motor/tranny mounts and front suspension will need to be upgraded for the V8 and drive shaft will likely need replaced, and you will probably want a beefier rear end in there.


This swap is not smog legal if that matters in your state.

smog is not an issue and it is a small block not a big block. I know about the radiator and the motor and tranny mounts and the power steering pump as i put this setup in an 82 grand prix and had to shorten the drive shaft. But wondered about wiring and anything else that might need done.


I only meant it as people swap in big blocks into these cars, so if those fit then so will your 400.

ok next question is can i use the parts i used to put this powertrain in a gbody to mount in the fbody. or will i have to get different mounts. also is the speedo electric or mechanical

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