Header Leak??

They were just the ones that came with an engine gasket kit that I had, I can't imagine that they are terribly good ones, probably the lower end ones. Definitely not ultra seal ones. And the only reason that I put the copper RTV on was because that's what the instructions said with the headers.

I have a set of dougs headers, so pretty good headers, the flange seemed nice and straight when I installed them, and I used some ARP header bolts, I don't know if they are locking or not.

When I broke the cam in I never checked how tight they were, but heard no leak (doesn't mean it wasn't there) and it only started leaking when I really started to get on it, so the headers were getting nice and hot, and I assume when they cooled off they loosened up, because when I tightened them some were pretty loose.