Hi Guys -

I am reworking a military 302 to go into my '54 GMC 2-1/2 ton dump flatbed. I actually bought two old 302s in various states of teardown and borrowed parts to make a whole engine. One of them had a coolant bypass tube going from the thermostat housing back to the rear portion of the head near the water temp sender, the other did not. My guess is that this is designed to prevent a big temperature gradient down the head and more evenly cool the engine to prevent warping and the like. The existing tube is crimped and will need to be replaced - I take it it's pretty important? (The tube is labeled 'AZ' in the exploded diagram that is first to appear in this site:

http://www.alfaheaven.com/MilitarySection/M135Mech.html)