Can't find a suitable rocker arm for your obsolete, exotic etc. engine?
I've written an Excel .xls program that predicts the dimensions and ratios of possible rocker arms based on their overall working length: the distance between the centers of the valve stem tip and the pushrod relief opening of your engine. The exact fulcrum/shaft center/trunnion location will depend on the ratio selected.
Adjustable sliders allow length selection, then another slides to select ratio, which returns both valve-side and pushrod-side lever lengths in Imperial and metric.
