OR,you could find some teflon type string packing, put it in thru the spark plug hole, and roll the engine over. the teflon is soft enough to smash if you don`t have enough clearance. we used to use 50/50 lead type solder on them yrs ago, it even worked w/o bending the valves. if it smashes down between the valve and piston, u can mike it w/ a certain degree of accuracy, but not 100%. will tell u if u need to be worried or not. just an idea, might give u peace of mind---------bob