The nut on the back side of my cylinder head backed off, and resulted in a leak between the cylinder and water jacket. I have pulled the head and have a new gasket on order. I checked the head for flatness using a straight edge as described in the manual and as is standard practice), and all is good. If this were a car motor, however, I would still "kiss" the head to be absolutely sure I had a good sealing surface. What say the experts here: Is it necessary to surface a 426 head? I have a big bore (444) kit and am running 13.5:1 compression.