Inliners International Forums General Discussion Engines GMC

Is there any books or information on the GMC's. I just picked up a 302 GMC, Military,no fuel pump provision, enclosed carb, watertight connectors and plumbing, the crank is 10/10 and looks good .030 over on the bore and no ridge. no bell housing or flywheel. I need to find out if the 228,248,270 parts are interchangable and if there any aftermarket parts?-------------------Thanks Dave

The information for the GMC engines is scattered.The oldest book I have that mentions them is "How to Hop Up Chevrolet & GMC 6 Cylinder Engines" from1951 by Floyd Clymer. Next are Clymer's 1954 "Chevrolet Speed Manual" And California Bill Fisher's reprint of it in 1995. Both have sections on GMV & Buick engnes but certainly not much. The newest I have is Fisher's "GMC Speed Manual" from 1955.
Although there is a lot of information in these books it is old and a lot of the parts mentioned are no longer available. Many of the valves, springs, and ignitions available today were not around then. If there was ever a market ready for a new book this is it. Some new technology can be applied to these old motors. Sadly we are losing guys that know things that have never been written down or shared. I am not familiar with the military 302.

Hi dep . . .

There is a site that specializes in the military applications of GMCs found in CCKW and DUKW vehicles:
The GMC CCKW Page

The parts interchange between 248, 270 and 302 have been discussed on this site and over at H.A.M.B. Patrick Dykes' site has some info and aftermarket parts for GMC:
Patrick's

Jummy parts show up on Ebay now and again. But I am not sure about the differences between civilian and military GMCs so interchange would need to be established.

regards,
Keith

A lot of information on the web about converting a military 302 to civilian use. If you plan to put it into a civilian truck in summary: You will need a 270 6-bolt flywheel and matching starter and clutch. Can use the front dampener but need to move the radiator on the front side of the radiator support, or use a 270 front dampener and leave the radiator in place. Grind off the protrusion (boss) on the block just ahead of where the starter is located. 270 distributor will work. Drill out the oil dipstick hole. It is a two step drill size. You will need to find a 228-248-270 oil pan and matching oil pump. Generator bracket - a standard OEM bracket will bolt into place just fine. Water p8mps from a 270 even 248 will work...not sure about 228 but my guess is that it will work. You can cut out the boss for the fuel pump or leave it alone and use an electric fuel pump and put a dummy OEM fuel pump where it should be located if you want an original look. The head and manifolds can be left alone. Change out the front motor mount to meet civilian truck front cross member. This is most but not all of the easy improvements you need to convert it. Check out Stovebolt site or OLDGMCTrucks.com

Thanks, That is a lot of good information. We need a strictly GMC thread that can be found with a simple search. One that has all stock specs and all known modifications.

Thanks Gear Heads, I have a 261 in my '55 Chebby P.U. thinking about putting this in a Sprint Car frame and making it street legal. What do you think? The block, crank, and head casting numbers all match with the clubs GMC casting numbers site military numbers. I wonder if I can open up the fuel pump boss for a cam driven fuel pump and no it is not going back togheter stock.--------------Thanks Dave

The OEM mechanical fuel pump is cam driven. Yes you can open up the block / cast area to install this pump. On the military blocks this area was not used and therefore never opened. Don't count out an old school 302 GMC for a performance engine! A lot of information on the web. Also, how to's to install a remote full pressure oil filter system can be found at the OLDGMCtrucks site.

Yeah I know I did the Full flow on my 261. Do you have any idea what the compression is with the #2193983 Head?------Dave---Hunterdude Huh; just bought a Browning X Bolt Composite Stalker in Cal. 280 soon to be a Ackley.