The method you described is for the first time adjustments to get your engine running. If you do this adjustment again, you will just push the pushrod deeper into the lifter, not centering it. Find an old stamped steel factory valve cover and cut the raised portion directly above the rocker bolts out. Install this cover on one side and start the engine. Back off each adjusting nut until the rocker "clatters". Tighten it back up just until it's quiet. Then tighten down a 1/2 to 3/4 of a turn. Do this to all 16 rockers and they should be very close to centered.
That's how I've done it for years,
Scott
