Did I mention that this machine shop specializes in Fords??
The strange thing is that the third time they failed was with the bronze insert. These were Ferrera SS valves. They tell me that they put these seals on every head they do. Has any one used these pc seals on early heads with stock rockers? Maybe early heads weren't designed for this type of oiling, rather relied on splashing oil on the stems like with umbrellas?