Excellent and intresting points IvyMike!
dM/dt? I take it that M = momentum = mass * velocity?
So dM/dt = mass * dv/dt = mass * acceleration = Force.
The spring Force must be >= the force on the cam lobe = moving mass of valvetrain * acceleration profile of the cam lobe.
The idea of maximum 'controllable' mass is useful where the profile of the cam lobe is fixed, i.e. the acceleration is a constant. Thus we calculate the amount of mass that a given spring can control. Admittedly, this is a back of the envelope calculation, but it's really a useful parameter for us street racers that have to choose a cam out of a catalog (i.e. we pick our cam first to meet specs, then choose a combination of valvespring strength and valvetrain masses to meet our RPM goal.)
Interesting point about bounce (I) - wouldn't a good solution just be to move the natural frequency of the valvetrain significantly above (or maybe even below) the excitation frequencies of the cam profile? Or to add damping to the system? Does this still happen a lot with hydraulic lifters/rockers (which provide some damping)?
Great point about bounce (II) - I never really thought about continuous higher order vibrations in the valvetrain. What is the primary cause of that? Large-scale camshaft vibration? When are you most likely to see it? Can you actually use these vibrations to help cancel valve bounce, i.e. carefully design a system so the higher order harmonics are 180 degrees out of phase with the fundamental? Or are they usually completely uncontrollable?
3y30wnj00 - nope. I design microchips for a living. IvyMike is a real-life automotive engineer though.
