[Rick Parker]

This is a very critical part of the valvetrain geometry. As Gaz64 said the contact pattern should be centered on the valve stem. Mark the end of the stem with a felt pen and install the rocker and pushrod of choice & run it through 2 complete revolutions and check the mark on the end of the stem. Ideally it sholud be perfectly centered, if not valve guides will wear abnormally. Vernier calipers are a good tool to use for measuring small variance. Longer pushrods move the pattern towards engine centerline, (intake ports), shorter ones move the pattern towards outside (exhaust ports). Take your time, this is important stuff. Using an adjustable length pushrod will allow you to "Move the pattern" then measure the pushrod for correct length.