This page describes how to properly install or adjust SBC Chevy Rocker Arms. There are many ways to set Rocker Arms and this is the way that works the best for me !
Set the timing mark to 0 TDC #1.
Once you are sure that the engine is at #1 TDC the following valves/rockers can be adjusted:
Note: If you are working with an older engine or used lifters it's possible that the lifters bleed may off pressure. (soak lifters for 1/2 hour in clean engine oil before installation.) You can improperly adjust your valves/rockers if you are not aware of this. You should have oil in the lifters to to get the most accurate setting. If the lifters have bled off their pressure than they will compress slightly after 0 lash is reached. (Once reaching 0 lash you can push the rod end of the rocker with the palm of your hand.... this could make finding 0 lash tricky !) Rockers can still be adjusted - just remember that ZERO LASH is achieved as soon as all slack in Lifter-Rod-Rocker is removed !
** Beware of using a socket that makes contact with the rocker arm in ANY WAY.
** Most GM Factory Shop manuals I've read call for a 1 full turn adjustment past 0 lash. Many aftermarket rocker arm companies call for 1/2 turn for final adjustment. A Rule of thumb I use is that if the all parts are new the adjustment is a a bit smaller and if the parts are used the adjustment is a bit larger. I have always had good luck using 3/4 of a turn, but I also re-use a lot of parts !! follow the instructions for your exact parts to be sure !