my new project is putting a 90 5.7l into my 89 in place of my 307. i want to replace the tbi with a carb. are these engines the same as the chevy 5.7? cause im getting ideas for carb and manifold but im not sure where to look.

Why would you want to go back to carb'd? The tbi engine is much better than the 307's unit.

well i agree. i love tbi and wanted to keep it. but i dont want to get involved switching out the whole wiring harness on the car. with the digital interior other differences it will probably be to involved. down the road i want to put on a stand alone tbi system on it.

Use the Olds 307 carb and emissions, it likes 350's just fine, been there, done that. Ran great.

Carb, TBI, 6 of one, half dozen of the other. TBI is a little better, but not much.

Use the Olds 307 carb and emissions, it likes 350's just fine, been there, done that. Ran great.

Carb, TBI, 6 of one, half dozen of the other. TBI is a little better, but not much.

really? i wouldnt even think of doing that. makes sense though. thanks for the suggestion!

I yanked my 307 out (broke a piston) and dropped in a stock 77 Olds 350, kept all the same except the air pump (heads didn't have the ports) and the ECM was completely happy. The only issue at all was went I put in the larger cam, it was hard to get enough timing to make the cam as drivable as it should have been (204/214 duration) and have it not ping in the mid range rpm when EGR was in. I had added the Hooker GN Turbo cat back (minus the cat) duals and reduced backpressure enough the positive backpressure EGR didn't work at the right time, so I swapped in a valve from an older Olds (I think 73-76 Olds 350-455 without California emissions) that was a ported only valve. It worked better, wasn't perfect, but better. The larger cam really needed 93 octane due to the pinging issue. I really overall just needed a ECM tune on the chip with a custom timing map, but I didn't have a way to do it then.

So, nutshell, if keeping stock ECM with the Olds V8, keep the cam LESS than 205 degrees on the exhaust and 196 on the intake to keep this issue at bay. The 307 HO cam is a good choice still. Even the IROC cam is a bit big, stick with no larger than the LT1 B/D Body cam if a small block (which is a great torquey cam for these heavy cars and a small block 350).

awesome advice. for now i want to keep everything stock on the 350. minus the smog crap. im gonna find manifolds for it without all the smog ports and get rid of the pump. but new cams is always an option

A chevy 350 isn't the same and isn't a direct bolt in like a Olds 350, but shouldn't pose much issues in getting installed. Trans should be dual bolt pattern, Grab some chevy motor mounts, relocate the fuel line (pump is upside down on Chevy), and completely new exhaust up front, as Chevy exits different than Olds. LT1 manifolds would be a good choice, headers better, but not as long life as manifolds.

If you lose the computer, you will need to lockup your own torque converter, and then anything goes for cams....

the 350 that came in the 90 fwb, are they chevy?

The only 5.7L that ever sat between the fenders of a Fleetwood/Brougham was a Chevy. The first 5.7L in a Cadillac was a fuelie Olds 350 that made 180 hp.

So my money is it is a Chevy V8 that you have or are getting.

If it was me, and I had the engine out, I would toss in a stock LT1 cam from a Caprice/Impala/Fleetwood/Roadmaster. It is a nice cam and makes great torque, and toss on a set of Vortec 350 heads, but you will need an aftermarket intake or modify your own to bolt up to the Vortec heads, but the gains would be well worth it, to the tune of a solid 240-250 hp with a very flat and fat torque band. Probably go with a nice roller chain, then I am sure I wouldn't let the grinder sit idle either.... It calls to me....

But that is if it was me doing it.

The more modern the cam, the better, the LT1 B/D cam is a good one for emissions too. Makes great low end torque for a chevy....