My old stock stamped valve covers on my 454 were leaking a bit and instead of just replacing the gasket, I decided to buy a set of O ring type valve covers. I bought them on e-bay for around $20 which is what used sets seemed to be going for. Anyway, they came with the used gasket (which looked to be in good shape), so I decided to put them on and they leaked like a sieve. Okay, I decided to buy new gaskets. That helped, but they were still leaking. Next step was to use some RTV. I used a thin coat and again it helped, but the problem was still not fixed. Alright, if a little is good, more is better. I decided to cake on the RTV and they’re still leaking. The valve covers are not cracked or warped at all and they heads look normal. Any ideas what I could be doing wrong?