440 valve cover leaks???

My dad had put some of the M/T or Holley cast aluminum (black with aluminum fins) valve covers on his Superbird. We put 7 different gaskets on them, including Fel-Pro neoprene and they still leaked. Someone told us that it was the valve covers, so we bought a set of chrome stamped steel (like stock, but chrome) and they sealed the first time.


There seems to be an issue with some of the cast aluminum valve covers sealing on a big block Mopar...