Hey I just bought a 79 cutlass supreme with a seized up 305 motor that I want to swap out for a 350. I seen on here that the 305 are Chevy motors that were put into the cutlass and I just wanted to know would it basically be a clean swap if I drop a 350 in it, or what would I need to make it happen. Such as new motor mounts, oil pan, harness transmission and or transmission mounts etc.. I really want to make this car come back to life and make it my daily driver. I’m just really excited to get it up and running. I just don’t want to jump into something blind. so if you guys could help me out I would greatly appreciate it.

 

Welcome, let's see some pics.

 

If that car also came with an optional Olds 350 (I am not sure) the swap should be fairly easy, if it didn't you may have some troubles with things like motor mounts, radiator shrouds, etc. I am sure someone here has been down this road before and will help you out. Good luck and welcome to the site.

 

Welcome! Too bad about the engine, hope you get it sorted out.

 

Post a picture of your engine and we can tell for sure if it is a Chevy or an Olds 307.

 

Cool, welcome aboard.

Yes, sort of tricky.... Not necessarily optional on a Supreme, 305s were maximum. But the 1979 R code Hurst Olds and 1980 442 were Olds 350s. All of which are the same body. So should be very doable. Although sticking to a Chevy engine is easier.

 

 

It is a Chevy engine. I would just replace it with a 350 small block Chevy. There is a large variety to choose from. It is a bolt in.

 

These are the same cars as the later 307 powered cars. Frame mounts from a 260 powered 78 to 82 Cutlass or a 81 to 88 Cutlass 307 powered car will definitely work. You can build up a nice Olds 350. Or drop in an Olds 403. The 455 will drop in on the 307 mounts but will need a drop in but has limited air cleaner space to fit under the factory hood.

 

Even though I believe an Oldsmobile should have an Oldsmobile engine, small-block Chevrolet is the easiest route here since it appears to have been born with the 305. Everything's the same, motor mounts, accessory mounts, electrical, fuel system. Easy peasy. Pull the seized 305 out, clean up the engine bay, set the new SBC in place.

Chevrolet 350s are a dime a dozen and they're decent engines with good parts and aftermarket support. I would not waste time with another 305 except maybe to salvage the heads. Some 305s actually had pretty good heads.

Just make sure you're actually getting a 350 or even a small-block 400. It can sometimes be tricky to tell exactly what a Chevrolet engine is, and in addition to the 305 there are also 262 and 307 ci (not same as Olds 307) versions to be aware of. I'm purposely leaving out the 265/283/327 family of SBC since they haven't been made in 55 years.

 

Just noticed car has a California plate. Are you in California? If you are their emissions laws are gonna complicate swapping anything but another small-block Chevy. You may have to transfer all the emissions devices and smog pump piping to the new engine too.