I would say aluminum dissapates heat way way faster than steel. If you weld a piece of each at the same time same heat you will see why. We welded a dominator flange on my dove spider intake and the whole intake was so hot it could not be touched for awhile. On the water flow issue, I have heard that in some stock classes the are reversing water flow so the colder water hits the heads first. I would assume so they can add a little more timing?