I have copper head gaskets in my mustang, o-ringed too. The motor was built by Dugan Racing in GA and the gaskets are Milodon (sp). By no means a Viper but Ive put over 120,000 miles with 9psi and theres no leaks whatsoever. 1 block, 2 sets of pistons, 3 sets of heads, and 4 rebuilds LOL - and...