big block chevy steel core valve cover gaskets speedway motors these premium quality big block fits chevy (bbc) valve cover gaskets are made with a stainless steel frame sandwiched between durometer-tested neoprene rubber. this eliminates leakage caused by internal pressure fluctuations. steel core valve cover gaskets won't tear or collapse. steel core improves seal. reusuable. .175" thick. fits 396, 402, 427, and 454 big block fits chevy engines. package of two gaskets.