rotator types, morning sickness, wobble test
Very interesting links, that explains the difference, thank you.
I can't help but wonder if the "morning sickness" that seems to be a Lycoming phenomenon, might have a correlation to the valves only being allowed to rotate rather than having a positive rotation design. Perhaps a valve that is being positively rotated will better keep clearance between the guide and stem? It would be good to know if there is any correlation between not rotating and failing a wobble test. One way to monitor rotation would be to see the valve in different positions, from one bororscope session to the next. Unfortunately, looking back through my last two sets of boroscope exhaust valve pictures, I don't see anything unique on the valve face that carried over from the earlier session to the latter.