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There are two different problems associated with hydraulic lifters at higher RPMs:
1. Lifter pump-up. When engine RPM exceeds the ability of the valve spring to control valve motion, the valve floats. The hydraulic lifter sees less pressure and more clearance. It "pumps-up" to the maximum of its travel. When the valve comes back in contact with the rocker, it is held open by the maxed-out lifter travel. More spring pressure and better lobe design postpones this effect.
2. Lifter collapse. To try to control the valves at higher RPMs, the valve spring rate is increased. At some point, the valve spring rate and lobe intensity overcomes the oil pressure in the lifter and pushes the piston to the bottom of travel.
In either case, the only real answers are:
1. Stop winding the juice lifter motor so high - it ain't made for that.
2. Get rid of the juice lifters and go with solids. Racer or poser? - the lifters are the difference.
thnx, jack vines
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