clutch

I have a clean 1987 olds cutlass supreme with a 307 engine that runs very well but has little power. My question is I'd like to swap out the 307 with a 350 from a 72 camaro with its 350 trans. What kind of mounting problems might I have and will my stock driveshaft bolt up to this or is this a no go from the start.
Another option I was thinking about is swapping out the heads with 350 heads and replacing the carb. Just looking for a little extra power.

thanks

oldcutlass

I don't know how much the 350 heads on a 307 will gain you. I do know that your SBC swap with T350 is fairly easy, but you will have to swap the motor mount frame brackets. Some of your wiring may or may not need to moved and I would recommend getting all the accessory brackets with the SBC. Your driveshaft should work.

Olds_71_442

The earlier Cutlasses from '81 to '84-5 usually had a 305 or 267 Chevy in them so it shouldn't be too difficult to find everything to change it over to Chevy.

I used to have a 400 sbc in one of my old G body Cutlasses and outran the RCMP with it more than once.

joe_padavano

Changing heads on a 307, especially a roller cam late 80s 307, won't buy much. Dropping in an OLDS 350 or 403 is the easiest upgrade, with a 455 swap only slightly more work (mainly exhaust and accessory bracket changes). The Chebby swap has been done (even by the factory, as noted) but there are a LOT of little detail things that change like motor mounts, frame mounts, starter, accessory brackets, wire harness, radiator, exhaust, etc, etc. It's certainly doable, but the fact that you already have a motor does NOT make this the cheapest way to go.

clutch

Thanks for the reply. Since you said I already have a motor and am looking for just a little more initial power what might you suggest for some better performance. I've thought about changing out the rear end gears and having the carb reworked. It's a clean car with a good running motor (70000 miles) but I can't take the snail like low end performance.
thanks

70W-32

By all means, change the axle, you probably have a 2.14 or 2.56 ratio in a 7.5 housing. Crappy gearing unless youre looking for MPG.

If you can find a 84-87 H/O,442, or GN/T-type rear axle, they have 3.42 or 3.73 gearing and are a bolt on.
Your car should have the 2004R transmission(overdrive), so even with the steeper gearing, so highway cruising will still be possible.

The most cost effective thing you can do to the 307 is to tune it up to its best performance. It takes a lot of properly spent $$$$ to squeeze more hp out of the 307, so just make it run good(theyre reliable and torquey), and upgrade the axle and change to a full dual exhaust.

then, if you want more, get a 350-403-425-455 Olds and swap out the 307.

OLD SKL 69

Welcome to CO! I think you were already given some good advice so I'll just add that its probably easier to put in an Olds 350, if you want to keep the CCC system intact and looking stock. It will run well with much better power and decent gas mileage. (I am thinking about doing this in my 85 Riviera that has a 307 Olds engine) If you don't care about it looking original, it's still easier to just drop in an Olds 350 or 403. Everything bolts up and you can get rid of the smog pump, and the computer controlled carb and distributor.

g_right99

Did you find a 350 motor yet? would you like to sell the 307?

425mann

81 Oldsmobile motor swap issues 307 to 425 motor mounts

oldcutlass

Use the 307 engine mounts to mount the 425. Click on the link below.
https://classicoldsmobile.com/forums...tion-list.html