Oldsmobile Forum - Oldsmobile Enthusiasts Forums - How much play should I have in my rocker arms?

Trying to do a valve adjustment. 72 heads on a 68 rocket 350. I have a hydraulic flat tappet cam. I am following this procedure: on compression TDC, tighten rocker arm nut until you feel first bit of resistance in push rod as you spin it between your fingers, then tighten the nut another 180 degrees, then tighten allen key nut. At zero lash, some rocker arms are already almost fully tight and I cannot go another 180 degrees, others still have room left to go after the 180 degree turn leaving the rocker arm a little loose. Which is correct? Why do some tighten faster than others? Should there be any play side-to-side in the rocker arm at all? Can the nut be over-tightened? Thanks for the help!