valve cover gaskets

I like the cork composite ones. I clamp a long 3/8 extension in a vice and use it as an anvil to straighten out the bolt flange area with a small hammer. I glue the gaskets to the valve cover with 3M weatherstrip adhesive after cleaning the surface with brake clean and then wipe a very thin film of high heat silicone on the surface that contacts the head. This allows for reuse several times. On engines with the stock cast iron manifolds that come close to the covers the cork is not such a good choice when they see alot of driving. The cork will become hard and crack after a while.