Rocker arm adjustment
 

I've got a 72 SB350 with 101500 miles on her. The lifters were replaced 5000 mi ago. (25 years ago)... she sat in a barn for a long time. There's a clacking when not accelerating that drives me mental. Sounds like rockers to me, like maybe they were poorly adjusted from the get go. Local Chevy guys said get a spare rocker arm cover and cut out the top, and adjust them while running. Is there anybody out there that can give me some input as to how I should go about this... or if I'm going in the right direction. She runs strong... but I don't want to damage anything. Thanks in advance.

Re: Rocker arm adjustment
 

I modified a valve cove in a similar fashion as was suggested. It eliminates the oil mess when adjusting valves with the engine running. This is a picture of my "prototype" valve cover. The final version had better hole alignment.

Re: Rocker arm adjustment
 

I've adjusted lash with the engine running, nothing wrong with that method but IMO you get better results with the engine off. Pull the covers & the plugs, set on TDC #1 on compression stroke (intake valve was the last valve to close), adjust intake valves on 1,2,5 &7; adjust exhaust on 1,3,4 & 8. Rotate 360° #6 TDC on compression stroke (intake valve was the last valve to close), adjust intakes on 3,4,6 & 8; exhaust on 2,5,6 & 7. Done with one revolution of the crank.
to get the proper lash, adjust rocker to zero lash, you can spin the push rod with your fingers to feel this. Then tighten an additional 1/2 turn (there is room for play here, some go less, some might go more, if you want to get real picky you can count the turns until your lifter bottoms & set pre load in the middle, I don't like bottoming the lifter to count turns so if I'm building a motor I'll use an old lifter, otherwise I just go 1/2 a turn)

Re: Rocker arm adjustment
 

x2, I have some like that with the holes lined up better, you can also cut out the entire section,not just the holes, then,while engine is running at idle, back off one rocker at a time,slowly turn the nut counter clockwise until it chatters loudly,now slowly turn clockwise until it is quiet,then slowly turn an additional 1/4 - 1/2 and you're done....on to the next...

Re: Rocker arm adjustment
 

This method works great, just used it today installing roller rockers and pushrods.