I'm sure you looked but is the case return hole clean?I have started up my panhead and I have had to take apart the front head because its over oiling. The gasket wich I have changed two times is breaking at the same place and that is at the return oil channel. The rear head is running perfect. It seems as the oil is not returning back through the channel, I have checkt the channel and its not plugged, I have checkt both the head and the cylinder. Before I started it I changed to new pistons +.050 and Jims lifters +.005 I suspect that I might have to go down to +.040 piston on the front head.
Does anybody know what the problem can be?