Hey everyone, I bought an old 1944 CCKW Army truck last year and discovered that someone had put a 302 in the truck, I think out of an M-211. Last Fall I tore it down assuming that it needed to be overhauled and found that its almost a new engine - time wise.
After reassembling the engine and starting it I became curious about the history of the 302. Ive played with 216s, 235s, 248s and 270s all my life but know very little about the 302.
I know that there were Military and Civilian versions of the 302 and that its a square engine - 4 inch piston with 4 inch throw but what was the year span that they were made? I have read 1951-1959 and 1952-1969, it doesnt seem logical that GM would discontinue the 302 while the 270 was still in production or that they would continue to build it after 1962 when the 292 began production unless under Military contract.
Would love to learn any history that anyone has on the 302 from concept to production timelines or anything else.
The 302 was developed for military use in 51 or 52, but it was introduced in civilian trucks at the same time and was produced through 1959. Both models used the same crank and pistons. The military had provision for a large motor mount in the front part of the engine. The civilian used the same mounts as the 270 of the same year. The military did not have a hole in the block for a fuel pump, but the cam had a lobe for it and a hole can be made using a gasket as a template. The military used an auto trans and had a different starter arrangement. There is a locator boss on a military block that has to be ground off to accommodate a civilian starter. A civilian flywheel housing and 6 bolt flywheel bolt to the military. The military used a sealed 24v ignition system which is usually replaced with a civilian ignition system. The military has a carb with a snorkel to keep water out. This can be removed leaving an intake manifold with a 4 bolt pattern that will accept a WW Stromberg. The 302 was replaced by the V6 family of engines in 1960. The 270 was still built until the early 60's for use in step vans. This was probably done because the step van builders didn't want to re design the dog house to accommodate a V6 and it was probably thought that the 270 was more economical than the 302 in a step van. The 302 is a very stout engine and is capable of putting out a lot more than its factory rated 145 HP. I have been tinkering with them for over 50 years.
The 302 gmc engine was the king of the drag strip and salt flats in 1953 and 1954. It was one of the largest displacement overhead valve gas engines of the early 50s. There were other large engines out there, but it was hard to get a Packard or Cadillac V8. In contrast, the 302 was readily available in dump trucks... although I'm not sure if the early hotrodders stole the engines from them, or got them legitimately from the gmc dealership.
Military-surplus 270's were popular with the dirt track racers my Dad ran with in the late 1940's and early 1950's. We ran well-modified flathead Ford V-8's on alcohol, and didn't have a lot of problems outrunning the 6-cylinders, but if the GMC's ever got hooked up well and avoided getting a lot of wheelspin off the turns, they could almost run with us. The 302's didn't come along until somewhat later. Their main advantage was more torque from the same external-size engine as the smaller-displacement GMC's. Jerry
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