Small Block Valve Lash

if it's hydraulic there is no lash. Rotate the until both the intake and exh valves are closed. I'm assuming you have adjustable rockers. Then grab the push rod with your fingers and spin it as you tighten the rocker adjuster down. Once you can't spin the push rod then give it a quarter turn. This should pre load the lifter. Complete this step on all 8 and your done.