Very informative, thank you. I still have not torn them down so dont know why the valves would lock up on the guides, overheating maybe? Lack of oil? Also noticed the pc seals on those two valves are coming apart. None of the valves appear sunk in so Im hoping I can get away with just grinding the seats. I expect to replace a few valves and guides but it seems like wishful thinking, may have to file 13 them and start looking for another pair.