Valve seals

[RustyPile]

Something that has been overlooked in this discussion.. Your heads appear to have had extensive valve guide work performed in the past.. From the factory, there are no guides installed. the guides are drilled directly into the head and the valve "rides" against the head.. Over time these "holes" (guides??) wear and the valve becomes loose in the hole. The hole can be knurled (tightened), but that's not a good solution as the knurling soon wears away.. The holes are bored oversize and guides are pressed into the head. My guess is the heads were machined for PC seals after the guides were installed.. In every picture, the replacement guide is visible.. The seals are designed to fit on what's left of the head protrusion above the spring seat, not the replacement guide.. This area is thin and has broken away, leaving nothing for the PC seal to fit over. This probably is not due to bad machining so much as bad quality control. Somebody didn't inspect the work before installing the PC seals. I came across this breakage a lot back in the '60s and '70s when I was building race engines.. This can be repaired by replacing the guides with ones of a different design but the procedure is expensive and should only be done by someone who knows exactly what they're doing. for pretty much the same money, you can replace both heads, their service life is over.