Ferrea valves has a very informative video of Spintron fixture generated images of spring surge, rocker arm, and pushrod failures, and is totally recommended viewing for engine builders! My favorites are: spring surge so violent that the spring actually lifts from its seat, and that is while the spring is at max lift! Early attempts at manufacturing carbon fiber pushrods that will function flawlessly at 9300 RPM, but fail catastrophically at about 6800 rpm, (used in NASCAR engines, they failed during caution laps, not racing!), they refer to that resonance phenomina as a "fuss point". That video starts out at 9200 rpm and slowing down the rpm. The carbon fiber pushrod explodes into dust and filament at about 6800! Fuss point, I guess! That's why I always inspect used springs upon removal. I have seen springs with shiny marks on the coils from touching, but the installed height allows for higher lifts by more than .100". We are all still learning. The video may be available from the sales staff. My copy is on VHS!!! It is required viewing for my staff. TIMINATOR