Join Date: Sep 2000
Location: Washington, Michigan USA
Go69 has the drill down pat - I've always done exactly the same thing, have never leaked a drop from LOTS of SBC's. The leaks lots of guys get aren't from the gasket-to-head, they're from the gasket-to-valve cover joint. If you could see inside the valve cover with the engine running, you'd see oil POURING down the inside of the outer wall of the cover until it got to the inner edge of the gasket that sticks inboard from the corner of the cover where the flange is; the oil is trapped (like a dam) and builds up here, and tries to soak out through the joint between the top of the gasket and the bottom of the flange, and the excess runs over the inner edge of the gasket and runs down onto the head surface where it belongs. Getting a good seal between the top of the gasket and the flange on the cover will stop the leaks, as long as you don't over-tighten the valve cover bolts (which causes leaks between the bottom of the gasket and the sealing surface on the head). If you'll look at the later center-bolt covers (which were designed as part of Chevrolet's "Dry Engine" program), you'll note that the new design carries the inner wall of the cover down BELOW the level of the gasket, then turns back UP to the gasket area - this lets all that oil pouring down the inner wall of the cover run straight down, uninterrupted by any gasket edge, and off the bottom of the curve of the cover into the head area - the gasket never sees any direct flow of oil. Since the older covers don't have this feature, the name of the game is to seal the area that sees the direct oil flow, which is the gasket-to-cover joint.
'69 Z28 Fathom Green