Well, these are brand new Billett Specialties valve covers and I used these $60.00 Felpro gaskets. Everything seemed OK at first, but after about 6 months they started to leak, just on the left side at the rear. Felpro says not to use any sealer on these gaskets. They are the the metal impregnated silicone rubber gaskets. It just seems a bad design that has been an enormous headache over the years for operators of SBC engines that has required of mechanics to try and come up with an ingenious way of trying to prevent them from leaking. It really seems as though from a design point, a few more bolts evenly spaced around the perimeter and there would be no need to even be concerned about leaks.