If the valves are hanging open then you need to shim the rockers. What brand and type RR's do you have. You should tighten the bolt/nut while twisting the pushrod with your fingers, when you can no longer easily turn the pushrod (0 lash) it should be 3/4 to 1 1/2 turns to torque spec on pedistal and the same and tighten the nut. This should properly set preload.