Best 383 valve cover gaskets to stop all the leaking

69_340_GTS said

If you try to use rigid cast aluminum covers on stock heads which are often not machined, you can almost never stop the leaking. In that case use stamped sheet metal valve covers and install them like RRR showed above.
If using cast/machined covers on machined heads, well they really should never leak. I like those Moroso Perm-Align gaskets with no sealer at all.

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That is only true if the cast/machined covers are made correctly. Mopar Performance made a lot of cast covers that are too wide to seal correctly and there is very little that a person can do to solve the problem. The faulty MP covers will tear a Moroso gasket to shreds very quickly. Sometimes the thick FelPro gasket can provide a seal between the head and the cast MP cover but not always.

I did a lot of investigation into valve cover leaks a few years back and figured out the problem. It all has to do with vendors make bad parts. If the parts are bad then the guy doing a backyard build doesn't have a fighting chance of making it work.