[rage'nrat638]

The adjustment is 1/2 turn down from zero lash. (GM MANUAL SAY'S 1 TURN)

In order for the hydraulic lifter to work correctly, it must be centered.
If your valves have come out of adjustment after several thousand miles of
operation, suspect your rocker arm nuts, and replace them. They do wear out
after constant adjustments.


When adjusting your valves, tighten all adjusting nuts until all lash is
removed by feeling the rotation and up and down movement of the pushrod. Next, set your engine on
TDC #1, pointer at "0". You can now adjust the following valves:


INTAKE on cylinders 1,2,5,7
EXHAUST on cylinders 1,3,4,8


Loosen the adjusting nut until lash is felt by rotating the pushrod. Then
tighten the adjusting nut while rotating the pushrod until all lash is
removed. Now tighten the adjusting nut 1/2 full turn. This "centers" your
lifter.


After you have adjusted the above valves, rotate you engine 360 degrees
bringing the pointer around to the 0 TDC mark. This is TDC #6. Adjust the
following valves in the same manner:


INTAKE on cylinders 3,4,6,8
EXHAUST on cylinders 2,5,6,7


Your valves are now adjusted properly.
good luck and may the force be with you
as per the g.m manual..