I have been rebuilding a 302 and have just put on my gasket matched performer manifold onto the edelbrock heads to find one side/end is about 1/8" too low when fully torqued down (but only @ one end ???. The other side seems to fit perfectly. Anybody got any ideas. I marked the top and bottom of the ports with a pencil line which ran to each end of the heads/manifold. 3 pairs of markings line up perfectly.