Vitos big bore compression

Ok I put another gasket on and run it then retension the head bolts whàts one of those leak down testers cost
 
I have used Copper Slip on the head gaskte thinking it would help the gasket slip on the barrel and head surfaces easier when it being compressed and thus achieve ultimate sealing, this proved the two times I did it to be incorrect as both times, the head began to blow and when i took the head off to check it out I found the nuts were almost completely loose. (All nuts were set to correct torque and checked after run-in)

Moral of the story, copper gaskets are do just fine as they are. No additives needed.