Damn header leaks! wtd?
Well believe it or not. The best luck I've had is with the stock type gaskes u get for exhaust manifolds. they have the perforated metal on 1 side and paper like material on the other. I put a lite coat of either red or copper rtv on both sides and let it set up about 1/2 hr before installing. I put the metal side out tward the header. I have no leaks and I'm useing 28 year old "blackjack" 89.00 headers on a small block. I learned this trick working on my dirt stock cars. I have even reused the gaskets with a new coat of rtv.