If you are readjusting hyds. the ones with spring compressed eventually bleed off. The lifters with valves closed hold the oil and will feel solid. When you adjust them, the springs will push excess oil out. Give them a minute or two to bleed off before rotating engine to make sure you don,t have a piston hit a valve. You have seen oil bleeding out watching the valve close on your dial indicator. Unless you have short travel lifters you will need way more than a half turn to center the plunger in its travel, more like two turns.