My last header gaskets leaked like crazy! They were Fel-Pro#1416's. I noticed when I removed them that the flange on the header did not seal properly, the gasket was actually too big. What do you use on your cleveland with 4v heads?
I used the FP #1416 with a little copper based high temp RTV and and they are sealed nice without any leakage. These manifolds were leaking like crazy before I did this. Did you check the faces on the manifolds to make sure they are flat?
1970 351c4v Convert
1974 HD WideGlide Stroker Shovelhead
1997 Lincoln Mark 8
2000 Dodge Durango(wifes)