Crane Cams 99380-16 Hi Intensity "Fast Bleed" Hydraulic Lifters (16 pieces) for

1962-1995 221" thru 302" & 351W,
1969-1982 Boss 302, Boss 351, 351C, 351M-400 &
1968-1997 370" thru 460"

Crane´s Hi Intensity hydraulic lifters produce a "variable duration effect". At lower RPMs this can reduce running duration by 6° to 10° and decrease valve lift by .020" to .030". These formerly called "fast bleed" lifters work best with a cam that requires more compression ratio than the engine actually has. They help restore vacuum, cylinder pressure and bottom-end performance. As RPM increases, Hi Intensity lifters act more like normal hydraulic lifters. At 2500 to 3000 RPM they will produce the full duration and lift of the cam.

They should be used only if the engine's compression ratio is below the minimum recommended for the cam you have chosen. These lifters can cause "low speed detonation" if compression is too high. They are slightly noisier than standard hydraulic lifters (but not as noisy as a mechanical lifters) with a maximum RPM potential of 6,500 to 7,000 RPM.