270/302 CRANKSHAFTS

joel gopan · Post by **joel gopan** » Sun Jul 31, 2005 1:38 am

The M-Series 302 Crankshaft will interchange with the WWII Crankshaft, it has same Rod and Main bearing Journal specs, along with same stroke. It does require the later 6 bolt pattern Civilian GMC Flywheel. Some Civ 302 Flywheels in mid 50s have the same depressed clutch surface. Finding the old parts to use are a problem though. After 1956 the interchangeability of Crankshafts and rods will be a pain, as the specs changed, and new late style rods are near impossible to find. I would rather stick to the original WWII 270, as when they are in topshape and well tuned, they give reliable service. Mine has plenty of zip, and Bob Rubino claims that his 270 powered CCKW SWB will outrun any orther CCKW in the Red Ball chapter, no matter what the power. If you can find a 302 to rebuild and install, go ahead, but there are a lot of details to contend with, and the parts are hard to find. It is a job for an experienced GMC mechanic.
Joel

armydriver · Post by **armydriver** » Sun Jul 31, 2005 11:30 am

As usual, thanks again for this information. You are a wealth of knowledge that we all need.

joel gopan · Post by **joel gopan** » Sun Jul 31, 2005 11:46 am

I am not so sure about that.
Joel

armydriver · Post by **armydriver** » Sun Jul 31, 2005 5:38 pm

Don't be modest Joel. You have helped a lot of people with their truck problems, me being one.. Thank you.

dr deuce · Post by **dr deuce** » Sun Jul 31, 2005 8:28 pm

Trying to find or rebuild some of the original WW2 parts is getting harder and harder.

If you put a 302 in your truck you will be quite happy, especially if you use the Chevrolet Corvette clutch and get rid og the "GMC clutch".

Manny Rogers is looking for a 302 for his mil DUKW that just lunched its engine.

Steve AKA Dr Deuce