I have a Set of the Cast Thunderbird Valve Covers on my 292. Replaced the Gaskets a few Weeks ago,.Still getting Oil Drips from the back Lower Corner. Covers are tight and Gaskets are not squashed. I seem to recall a few Years ago a Suggestion was made to build up that Corner inside the Cover using Ultra Gasket Maker to alleviate this Drip. I guess that Corner must get more of an Oil buildup until it Drains?. Suggestions?