Inliners International Forums General Discussion Engines 54 GMC 248 Engine Rebuild

Just picked up a 54 GMC 150-24 flatbed truck, has been sitting for over 40 years. I got 2 more spare engines (2-GMC including original one and 1 Chevy). The Chevy engine currently in the truck turns by hand. I'd like to see if it runs, or maybe just pull it. I don't have nor want to buy a 6 volt battery just yet.

I want to rebuild the original 248 and put back into the truck once I get it cleaned up and painted. Looking for advice as well as links to rebuilding this engine. Possible I can re-ring the engine, etc.
Any engine manuals out there to tell me the specs, etc.
Thank You

Your 248 will be a good strong street engine. Parts are getting a little harder to find but they are out there. Everything you need to know is in old posts on this site. The problem is they are almost impossible to find because the search feature here is a POS. Try doing your searches on Google, sometimes the posts here are easier to find with a google search. Once you find one start searching the posts of the guys who responded to that thread and keep looking. There is a lot here but it's all like a treasure hunt.
Here is a recent 248 build on the HAMB that went pretty far into GMC building.

GMC LINK

This book by California Bill Fisher has a lot of good info mostly as an add on to the Chevy six info. The bad thing about building these engines is that California Bill's book is the last one done on them so there is nothing new since '54-'55. There are lots of newer parts that will work, like some small block Chevy valves.

Chevy, GMC, Buick Speeo Manual

Thank you for the info. The engine I have appears to be complete. I am looking for a harmonic balancer to start. I am going to start taking the crank out so I can get to the pistons, think 1 is stuck. Hopefully I can reuse the pistons and crank. I think the truck has been parked due to a bad rear main seal. Seeing a LOT of oil that was leaking in that area. Hopefully that is the case. I am still learning. At least it's the original engine for that truck.
The engine that's in the GMC is a chevy, need help identifying what it is and year. Number stamped on side is 00II242F54X
No casting numbers other than CON1 K5 6

Just starting on the original 248 engine then I'll probably start taking the body off the frame so I can get it all cleaned up and any rust areas fixed. Just noticed 2 small holes on each corner behind front fenders where feet go. Hope simple fix.

The company Best Gaskets lives up to their name. The rear main seal and the valve cover gasket is worth the price for the full set.

The Chevy engine is probably a 235. It would have screws holding the valve cover on rather than the two studs through the top. The side cover on a 216 covers the entire right side from the valve cover to near distributer. Check the casting number charts here for help. The stamped numbers on the GMC near the distributer tell what the engine is. It's not that easy with a Chevy. It's possible you have the highly desirable 261 (looks almost the same as a 235) or even one of the later 194-292 engines. Pictures would help but that is tough here evidenced by the few pictures you see on this site. Keep us up on your progress.

Here are the photos,hope they help.
https://flic.kr/p/2jKaVMX
https://flic.kr/p/2jKaVyv

On the original GMC 248, have 2 stuck pistons. removed the crank. Other pistons came out nicely. Just the # 2 and 5 piston really in there. Used a block of wood and hammer, still no avail. Now soaking with more fluids. Fun, Fun, Fun...

That is a 235, Possibly but not likely a 261. Diesel, ATF, or citric acid and water will get it loose if you let it sit a while.

Been soaking the 2 pistons, was able to move them slightly but cannot get a piece of wood on the rod side, even cut a notch in the wood to fit around rod onto pin area of pistons. Ended up busting the wood in pieces. It's rusted or corroded between the rings is where I am seeing it stuck at.
Was wondering if I could make a fork out of steel and place around the rod onto the piston and use my hydraulic press to push out?
Unless there is a better idea?

If the rings have rusted the cylinder walls it is doubtful you'll get by without a clean up bore job. Try to measure the wear in a cylinder that you got the piston out of to see how much wear you have. If it needs to be bored don't worry about saving the rest of the pistons. The best penetrating oil I have ever used is a 50/50 mix of ATF and paint thinner or acetone. The ATF does not have to be new.
Soak a while, move a little, soak again, move again........it will come out. Don't get in a hurry and ruin something.