Is this a new or rebuilt engine???
If new or rebuilt, do the preliminary adjustment as stated by the guys in the last posts if that suits you.
If it is an engine with some miles on it(being ran and driven at all),remove one valve-cover and either use the anti-splash clips on the rockers.You can get them at a local auto-parts store for about $10.00.Install the clips on the rockers and with engine idling and warmed up to normal operating temp, start with # one rocker and slowly loosen the adjuster nut until you start to hear it clicking.slowly tighten the adjuster nut until the clicking goes away. then SLOWLY turn the adjuster nut 1/2 turn tighter.You are done with that rocker. do the same to all other rockers one at a time until you are done with the last rocker. install and secure the valve-covers and your valves are now adjusted
I never have used the 1 full turn on the adjuster nut, it is too tight!!! It will wear the cam lobes too much as the SBC engines are notorious for
I have had the best luck with 1/2 turn (no more than 3/4 turn).