I too was looking into 'thick' head gaskets as a way too lower the compression in my 455. Everybody I talked to that I considered knowledgable; in racing circuits, machine shops, etc...all said the same thing: NOT for street use! If you're racing, and you're going to be pulling the engine apart all the time, then copper gaskets are okay. But street use will kill them way too quickly; and I was told, "You'll have water everywhere." (Everywhere you DON'T want it, that is.) I was convinced; so instead of using thick gaskets; I'm using a new block!
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