When a hydraulic lifter cammed motor experiences valve float, how far open are the valves when this happens? Valve float can occur with any conventional valve train, ie hydraulic, solid, over head cam. Don't equate hydraulic lifter "pump up" and "valve float" as being one and the same; though similar, there are slight differences. Valve float is basically the inability of the springs to control valve action; inertia loads/velocity of lifter, push rod, rocker, valve and retainer over whelm the spring and the lifter/cam follower are no longer in contact with the cam lobe. How far the valves are open is dependent on how far are the lifters/cam follower is off the cam lobe. Hydraulic lifter "pump up" is thought to be when piddle valve inside the lifter body can not bleed off excess oil, thus the preload space is taken up with oil; this too will hold valves open.
Do both intake and exhaust valves float at the same time or do the heavier intake valves always float first? Where ever the weak springs are.
When does this condition cause contact between the piston dome and valve face? Thank you.
