Remember at peak tq which is near peak volumetric efficiency, the cylinder is full (or maybe even over full).


Since your on the compression stroke, the pressure in the cylinder is increasing..


So whatever pressure is on the backside of the valve is minimal, or at least very similar (offset) by the chamber pressure.



I've sucessfully run as high as 23psi with over 2:1 backpressure on a hydraulic roller without doing anything crazy.

I even tried shimming the plunger travel tight, and adding spring pressure searching for more RPM .... and it didnt do squat.

This was a 235@.050" .540 lift 6500 RPM combo.