FUEL-PUMP PRELOAD
Measure the installed combination
A fuel-lobe percentage does not automatically determine the cap.
Cam base circle, HPFP version, pump travel and the installed stack all affect preload and remaining travel. Measure the actual installed combination at minimum and maximum lobe lift before deciding whether a cap is required.
The inexpensive EN-51092-style tool locates the fuel-pump lobe’s base circle. It does not replace the installed preload and maximum-lift clearance measurements.
A cap that removes too much clearance can bottom the HPFP. “32% lobe = one specific cap” is not a safe rule.
Method reference: Fyreant’s LT1 lash-cap clearance guide. Tool reference: GM EN-51092-style fuel-pump installation gauge.
