"George Patterson" wrote

In the absence of some catastrophe, such as a bent pushrod, this is
generally caused by not flying enough.

Whenever I see less than 200 hours on an engine in a year, it seems like
there are tales of destruction of an engine to follow.

All of this would not be nearly as likely (it seems to me) if aircraft
engines were equipped with rollers on the cams.
--
Jim in NC