A little contact cement on the valve cover side, grease on the head side. Do not over tighten works for me. If they are OEM most head surfaces are rough and uneven.
I have aftermarket alum. heads, all smooth on the rail surfaces, I`ve tried about every gasket I`ve seen, and still have a little oily residue under the valvecover rail. I`ve cleaned the cast valve covers too, even have hughs non - burnable gaskets installed the way they recommend-----------
doesn`t drip tho.
right now anyway !
Wish the 440 blocks had the corner drain holes like the elephant !