re: Need help OT mechanics

New rubber would be superior, hands down. The reason for this is that it compresses better than cork. If you over tighten the cork, it will split. Try to tighten fron the middle out, as evenly as you can. I use permatex between the cover and gasket, essentially gluing the gasket to the cover. Then a thin coat of silicone on the gasket before you mate it to the head.

Biggest thing is to not over tighten the bolts. If you do it right, they just don't have to be very tight. If you see gasket squeezing out under the bolt, you've probably over tightened it.