I'm with tcelderman and deluxe54panel on this one. Most steel stamped valve covers are warped from overtightening them. The holes are certainly concaved from tightening. I take mine on a metal support and use a solid metal piece of stock and make sure they are flatened back into shape. Eyeball down the edge when the cover is upside down and you will see it plain as day. If it's not the valve cover, the gasket edge of the block is damaged. Try using some V8 valve cover washers to distribute the pressure. They don't need to be as tight as most people think.
Remember when you use goop, glue, or anything of that nature...as much goop that squeezes out when you tighten down the bolts also squeezes to the inside of your engine.
