It made all the differance in the world. When I had my valve cover painted, I did an extremely shitty job of putting the inside tins back together. Had the same prob. I cut out a new gasket out of silicone for the inside tin and put it back together! no more freaking issues . I played hell moving my oil catch can around. that and replace the pcv and moved vacuum lines, ect. Just wanted a good job on that gasket. Oh yeah, also the first manifold I had was like you are talking about. I could see into the thing. Finally have one from the new motor, with no cracks. (I will still have a header built.)