[Tim Ayers]

Originally Posted by tubman

I had the 327 in my Corvette rebuilt a while ago. When I got it running, it ran well, but would not idle for any period of time at all before it started to boil. I tried everything; changed the radiator cap, flushed the system, and a bunch of other things. I was just getting ready to pull it, when all of a sudden it settled down. Like the previous poster, I believe that it was built too "tight", and after it finally got broken in, it was (and still is) fine.

I'm not saying that this is your problem (flatheads have more cooling foibles than SBC's), but this is what I experienced.

Interesting. Maybe OP should run it hard to see if it cools down?