Leaky valve cover follow up.

I'm befuddled as to how that can happen with those gaskets. They are silicone rubber over a STEEL CORE. How in the world can they squirm out from under the valve cover rails? I would be removing those valve covers and inspecting them and the head rails VERY closely. Maybe even involve a magnifying glass and no I ain't kiddin. The idea that the valve covers might be making contact with something is a good one. I would look at the FULL perimeter where the valve cover rails sit down on the heads and make SURE they aren't hitting anything. Also, as mentioned, look closely on the intake side as lots of times the raised ports on certain intake manifolds will contact the valve covers and keep them from sealing completely.