These hydraulic lifter cams are capable of 6000-plus rpm with stock springs and no valve float. Excellent in the 2800-6500 rpm range. Designed for big-inch stroker motors with head work. Uses stock springs. Works with stock hydraulics, with stock spring travel set to .560″ minimum. Must check coil bind, valve-to-valve clearance and valve-to-piston clearance.. Made in the U.S.A..