Quote: No need to pull heads to measure valve to head clearance. Very easy to do with heads in place.
Here's my guess: Cylinder TDC, install weak spring, set depth gauge to top of valve stem and then measure total distance to contact on piston. Subtract known lift?
Starting a few degrees before and ending few degrees after TDC. Valve to piston clearance is not the closest at TDC but usually a few degrees after.
