On GMC 270-302 rockers;I measured the lift at the tappet and the valve several times.The actual ratio with the stock sheetmetal rockers is 1.41,most cam grinders list it as 1.5,so your losing a little lift in this case if you go by the cam grinders figures.
I also experimented with rocker geometry on the same 302 by altering the rocker position when the valve is closed by changing the position of the pad that contacts the valve stem.I found almost no difference in lift,maybe 10 thousands max at the valve.My final postitioning of the rockers was based on keeping the rocker to valve contact reasonably in the center of the valve stem.This was done on a cam having .440 actual measured lift at the valve.
