Jokster24

Hey all my olds fanatics I am swapping my 305 or 307 engine out of my 1988 cutlass supreme classic For a 74 hurst olds 350 rocket and what I need to know is will I have to change anything before I put my new engine in thanks?

J-(Chicago)

Yes. You need to swap the flare fitting and the metric fitting on the power steering pumps. Use the motor mounts from the 307 on the 350.

If you are not running the stock computer, there's more to do.

Jokster24

thanks but what else would I have to change if I wanted to upgrade from my stock computer

joe_padavano

Let's back up. The Olds 350 is externally identical to the 307. All you need to do is swap the water pump, accessory brackets, motor mounts, and exhaust from the 307 to the 350 and bolt it in. Don't even mess with changing flare fittings on the PS, simply use the stock 1988 pump on the 350. By keeping the water pump, accessory brackets, and pulleys together as a matched set you'll avoid the common pulley alignment problems. Also, pay careful attention to the spacers between the PS pump brackets and the block and be sure they go back in the same places.

As for computer upgrades, there really aren't any unless you want to burn your own PROM. The CCC system controls the primary side mixture ratio on the Qjet and timing in the HEI (as well as other things like the EGR valve, the EFE valve, carb vacuum break, evap system purge valve, and the A/C compressor clutch). If you want to retain the computer, you need to retain the original CCC carb and distributor. You're stuck with the primary side metering rods and jets, but since the secondary side of the carb is purely mechanical, you can swap the secondary metering rods from the carb off the 350. The CCC carb on the 307 has a stop that limits the secondary air valve plates to only 70 deg of opening. You'll want to file this to get a full 90 deg.

Of course, you can also eliminate the CCC system by swapping the carb and distributor for non-computerized versions. You will need to bypass the A/C compressor clutch function if you want to retain A/C.

Oldsmaniac

It is important to make sure you do have the 307 and not a Chevy 305 or else the swap will be a lot more difficult matching things up.

joe_padavano

Agreed, but unless the engine has been changed, the VIN Y 307 was the only engine offered in the 1988 cars.

Oldsmaniac

Ok, wasnt sure but did not some of the full size wagons get the 305 's around then?

joe_padavano

Well, the OP was asking about a G-body Cutlass, but the Custom Cruiser only got the VIN Y 307 as well. I can't speak to non-Olds B-body wagons, however my 86 Caprice wagon also has a factory-installed VIN Y motor. Frankly, I think ALL the B-body wagons were using the 307 at that time. The 305s were being used in the sedans.

Jokster24

Thanks everyone for the info. I will be using all of your advice and will be uploading photos soon