Even a "stock" rebuild of a GMC inline six can make a checkbook need CPR. After WW II there were untold thousands of GMC 270's sold for surplus, as a large number of 6X6 military trucks were built on GMC running gear. Sadly, virtually all of them, and most of the 1950's vintage military 302's got sacrificed to the gods of racing- - - -drag racing, dirt tracks, and even a specific class of Bonneville land speed record run that the 302 was used for. The surviving "go fast" stuff is being hoarded by a few GMC enthusiasts, like multi-carb intake manifolds, headers, racing cams, 12 port Wayne heads, and other bits and pieces that are mostly only good for all-out racing.
Fortunately, a basic stock rebuild is all a 302 really needs for a truck the size of yours. It's got plenty of torque to handle the load, and there's not much advantage to going for high RPM horsepower- - - - -that kind of engine build will dramatically shorten the lifespan of the engine! Piston rings, rod and main bearings, gaskets, and other regular rebuilding parts are still available with a little careful shopping. Pistons- - - -they're scarce and expensive, so don't do a re-bore job unless it's an absolute necessity due to taper wear in the cylinders.
The 270's Dad's 34 Ford 3 window coupe was running against on 1/4 mile dirt tracks in the early 1950's had plenty of torque, but not enough traction- - - - -he said his car would be halfway down the straight before they could get hooked up coming off the turns!
Jerry
I know youre the king of "if it aint broke dont fix it" but we are in a modern woels where a truck this size wirth maybe 150 hp/ 250 torque doesnt get up and go like it needs to. I have heard of the expense of building them but the motor in the black viking i posted is a downpayment on a house in itself. I also am not even sure what to expect out of a performance 302. We talking 200, 250. 300 hp? Ideally id like to keep all my power down low as it is a truck so a big cam doesnt interest me. What does is cylinder heads. And boost for this particular truck. A small turbo and a cylinder head would get me where i want to be. As far as power goes. Just not sure who to even talk to that does gmc performance. As ive reached out to sissels and they havent gotten back
