I have aquired a GMC 371 engine. Low miles but has years of limited use (less than 10k miles) and lots of time just sitting. The last time i was in an engine was a 56 caddy. I pulled the heads to check cylinder wear. The head gaskets had rusted away to nearly the cylinder. So i figure that all vintage engines are basically in sad shape regardless of compression incluging this engine. So the question is, always pull the heads or wait til it breaks? If yes to pull the heads, will the retorgueing cause oil burning due to distorting the block? What else to do with heads off? Or simply just rebuild and be 100 percent sure of everything? This engine will have valve rotators, are hardened seats a must with todays gas? Thanks for your thoughts and comments? This engine comes with a 4 speed tranny. I am not using it and will be going with the 55 hydro. Is the manual tranny setup of any value? i could use the funds for more engine work. Will the flywheel, tranny and parts help anyone with a 3 on tree? I don't have any GMC parts manuals, should i invest in them for this engine or will the Olds parts manual be all i need? I have the Olds car and parts manuals. Thanks. Ron

 

What is this going in? You have a 3 cylinder Detroit Diesel that hasn't run in a long, long time? What is your goal?

 

This is a vintage olds engine into a 55 98.

 

Ha! I was questioning the same thing! GMC had some 2 stroke Diesel engines that were 3-71, 6-71, 4-53 etc. 1st # was cylinder count, 2nd # was cubic inches of each cylinder. I think we are talking about a Oldsmobile 371 cubic inch V-8 in this thread. Not sure how to answer this question??..

 

List the transmission and all associated parts on some of the truck sites.

 

The tranny is probably a SM 420 if it has a granny low, We are talking about a 4 speed manual aren't we because they also came with a 4 speed hydro also? Depending on funds at the time I wouldn't drop a unknown engine with a unknown history in a car without tearing it at least part way down, I mean it is a 60 + year old engine that has probably had a hard life in a truck. There was a reason it was pulled the first time, maybe it was in a wreck or maybe it was just worn out It cost a bunch of labor to find out once it is back in a car. You never know if it has a spun bearing or a bent rod, rusted cylinders, it cold be junk....Tedd

 

Take that 371 cid Olds engine apart, it's the only way to find out what's going on in that old engine . I know it can be an expensive job since I'm rebuilding a 1961 394 Olds. I also have a 1958 Olds 371 cid bolted to a Jetaway automatic transmission in the corner for sale.

 

If you can't do a compression test because the engine is currently on a stand then do a cylinder leak down test instead.