340 Valve Cover Gaskets Leaking

Paladin: Had the exact same problem on mine. Started with a cork/rubber combined gasket, (Fel-Pro)then bought a rubber gasket (Victor), still leaked. Valve covers were good and straight everything was clean, even used non hardening gasket sealer, still leaked. Finally purchased a set of Mopar gaskets with the steel shim and coated on both sides with rubber. Took care of the problem. They are not cheap, but were probably cheaper than the other two sets of gasket I bought.