What do I need to change in my 1985 olds Cutlass supreme to change aa 307 to a 305

Dan Mcquade

Asked by Dec 06, 2015 at 09:20 AM about the 1985 Oldsmobile Cutlass Supreme

Question type: Car Customization

My Cutlass has a blown 307 in it and I can
get a 305 cheap that is ready to go pretty
much just need to know if I have to change
my transmission and motor mounts to do
this? Or will everything for the 307 work

7 Answers


She'll bolt right in there, but set it up as the old motor is.

Best Answer
Dan Mcquade

The 305 is a Chevy 305 will it still be OK


That could be different, Oldsmobile vs Chevy... It still might, I can't remember at the moment, If it bolts in you will be fine. If you can, it would be wise to compare the two looking for any differences before doing anything.


Ok finding out a few things, what side of the 307 motor does the starter bolt up to? The driver side? If so the Chevy motor will not bolt up. I went back to my archives...


I think the battery, fuel line, starter are on opposite sides. Up until 1981 Olds Cutlass' could have a factory-installed Chevy 305, after that came only with Olds engines. It will bolt in, and you should have the multi-pattern bellhousing so it should bolt up, the wiring harness is nearly the same, other than the battery/starter being on different sides, you'll have to make some modifications.

1 out of 1 people think this is helpful.

Putting in a Chevy 305 AND transmission can be done with a lot of work, The cross-member doesn't line up and and the drive shafts are different lengths. The Chevy will not bolt up to the Olds trany.


Because of the starter...

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