redline

[dinomite]

I believe that the redline is actually part of both of those, valvetrain and piston velocity. If the revs get too high two things happen: valve float and piston separation. Valve float is when the spring isn't strong enought to bring the valve down in time to get out of the way of the piston. A collision of this sort is nowhere near as serious as having a mismatched cam/high ration rockers/etc. Also, if the revs get to high, the piston will separate at the wrist pin, simply because it creates too much force going from one direction to the other. This can also happen if the connecting rod fails at the crank end.