Hoo boy --- lots of variations on this one. If it has the original factory style Pontiac valve train (rockers, studs, balls, nuts) then it's not adjustable. The correct installation is to torque the rocker nuts to the specified value (the exact value escapes my feeble memory at the moment). They "bottom" on the bottlenecked part of the rocker studs. That's with everything original, everything in good shape, etc.
However, if anything has been changed fro original (perhaps by a previous owner) or is overly worn (rocker nuts "loose" from having been installed/reinstalled a multitude of times, then that procedure may not work for you.
I'm a big fan of "poly lock" rocker nuts because of their positive adjustment capability. I'm also a big fan of replacing the factory bottleneck studs with the beefier 7/16's ones.
If there's any slack at all in that one pushrod as you've described, then that's going to be the source of your noise. Question is, why? Is it because the rocker is loose, a collapsed lifter, or something more bothersome such as a flattened cam lobe... That's to be figured out.
Also, the adjustment procedure GR described will certainly work - most of the time. If the engine has an aftermarket cam with a lot of extra duration over stock, it may not. If you want to be certain, use a wrench on the balancer bolt to turn the engine over until you see #1
exhaust value just beginning to open - then adjust #1
intake. Turn it a little more until exhaust valve #8
is beginning to open, adjust #8
intake --- and so on in firing order sequence until you've adjusted all the intake valves. Now start over with #1
, turning the engine over by hand until you see #1
intake just starting to *CLOSE*, adjust #1
exhaust... etc. until you're done. It takes longer, and your arm might get a little tired from all the hand cranking, but it guaranteed to be right if you're not sure what kind of cam you're running.