638montecarlo said:
Also what makes a cam over/undersprung? Of course the higher the rpm the higher the spring pressure but how do you know how much is too much or too little? Is there a formula on max rpm = a given pressure? I am sure that if you have too much spring pressure you will be wasting energy on the unneeded spring pressure and also the wear on the whole valvetrain. Also I am sure it has to do with valvetrain weight also, like a heavier valve requires a higher pressure spring to close it at a given rpm. I could go on and on!
That is why you have to take the manufacturer recommendation with a few grains of what you know of the rest of your valvetrain. Antiquated master lobe designs, and max performance profiles are really the spring killers. Improper spring pressures wipe out flat tappet stuff as well as rollers.
A weak/broken/improper spring or floating the roller tappets is what usually kills the lifter wheels and cam lobe on the roller stuff. The roller wheel must maintain a reasonable lash and follow the lobe closely.
I've run a hydraulic flat tappet with as little as 85# on the seat and 135# over the nose up to 5800 RPM's with steel valves and retainers.
Depending on the lift and profile, I'll have 125# to 135# on the seat on a mechanical flat tappet, about 300# up to 350# over the nose, the higher end for BBC and large intakes on a SBC to twist up to 7500
Rollers, big spread on what you need there again according to the cam profile, RPM range, and weight of the valvetrain on the valve side of the stud.
Weight on the pushrod side of the rocker stud means nothing, and actually, more is better in most cases.
My cylinder heads get each valve spring individually set up and charted. Valves are stamped for position, and each spring is checked for both seat and open pressures.