These tappets perform like a hydraulic tappet from start up to about 5.500 rpm and then turn into a solid up to the rev limit. What this all comes down to is that about the time your springs start to surge at high rpm and go into harmonic distortion the tappet rollers start lofting off the back side of your cam. With JIMS Hydrosolids you can be at ease knowing that they will not pump up allowing your valves to hit each other or the piston with consequent disaster. This is very critical in high performance engines with big valves and high lift cams.