cams STRENGTH of valve train and rotating assy balance are all factors in redline !

a cam can only rev so high and the spring can on return so fast before you get terminal velocity and it floats a valve and says bye bye !

internal balance consists of : Crank, Crank Pulley, FLywheel, ROds, Pistons. Weighted and Spun to balance everything is matched to the lightest component.

Head Basicly is stronger valves springs to can spring at the rate of the cam and RPM of the Bottom end. Your RPM is determined by the Speed your internals can spin and they themselves can rech terminal velocity but usually never does you usually get something coming apart due to vibration or imperfect parts.