dgc333 said

Stock manifold gaskets do not separate the center ports. When I installed the headers for the first time the gaskets that came with the headers had been folded and were damaged so I used the stock manifold gaskets that came with the Fel-Pro gasket set. Because they didn't have the center web the leaked like a sieve.

Most all headers eaders have a raised bead around each port and with out that center web in a stock manifold gasket you have an open path for a leak. They may work on headers without the raised bead but can't seem them working well on headers with them.

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