The Stovebolt Site Forums The Shop Area Driveline Need help with my '42 GMC

I have a 42 GMC with a 228 engine installed. I'm having a few problems that I think all stems to the fact that the carb is to a 270. When I bought it the guy though the shifting problem was from the engine sitting since 1982 and still using the fuel left in it. It ran a little “Slow” but sounded good. I put new gas in, engine cleaner and oil cleaner. The engine ran a lot better but it’s still having this problem. I think it needs ran some more too clean out the system, it gets better every time I drive it.

Problems:

High idle, I know pretty obvious, but the question is; is there some kind of attachment that I can add that restricts air flow down to 228 specs? Or do I need a new carb?

Shifting up from 2nd to 3rd it takes some time after shifting to regain speed. Going from 3rd to 4th I have to have a downward slope to keep the engine from slowing and stalling even with the gas floored.

Down shifting from 5th down when I hit neutral the engine reved extremely high and I had to kill the engine, I thought pushing it into 4th would blow the transmission up.

I am going to post this in both engine forum and the driveline forum because it seems it may be relevant to both.

down shifting from 5th? what size truck are you talking about. if it were me id do a complete tunig on it and get the carb worked on.

its a 2.5 ton military truck with the rear choped to a single axle