Looking at the TORSIONAL DAMPER you will notice it has three MARKS/LINES on it that are evenly spaced on the outside perimeter of the DAMPER. Looking closer you will notice one of the MARKS/LINES is wider than the other 2 (I have this one marked with white paint in the groove). This is the one you start with for setting up the No. 1 piston at TOP DEAD CENTER (TDC). This may be determined by placing fingers on the #1 rocker arms as the (wide) mark on the damper comes near the “0” mark on the timing tab. If the valves are not moving, the engine is in the #1 firing position. If rocker arms are moving as you come up to the line then you are on TOP DEAD CENTER for the #4 piston, all you have to do is rotate the wide mark all the way around (360 deg) and back to the “0” on the timing tab. Make sure you turn the damper in the direction of normal operation (looking at damper through passenger side rear wheel well, tire removed the correct direction of rotation is clock wise).
Once we have determined we are on #1 piston TDC we can now adjust both INTAKE and EXHAUST valves for #1. Correct adjustment per Pontiac service manual is: Back out adjusting nut until lash is felt at the push rod, then turn in adjusting nut until all lash is removed. (This can be determined by rotating push rod while turning adjusting nut). When lash has been removed, turn nut in 1 ½ additional turns. (This is to center lifter plunger).

NOTE: For stock setup 1 ½ turns IS the correct adjustment.

Now once you have adjusted # 1 valves it is really easy to adjust the others. Since firing order for the V6 is 1-2-3-4-5-6.

Now just turn the damper until the next MARK/LINE is in line with the “0” on the timing tab this will be TDC for Piston # 2. Adjust both Intake and Exhaust
Valves.

Turn the damper again stopping at the next MARK/LINE on the damper. This will be TDC for Piston #3 Adjust both intake and exhaust valves as previously discussed above.

Turning the damper again and if you have followed directions correctly you should be back to the wide groove that we first started with when we adjusted TDC for Piston #1 except now we are at TDC for Piston #4 go ahead and adjust both valves.

Turn damper to next MARK/LINE again and we are at TDC for Piston #5, adjust valves.

Turn damper a final time to next MARK/LINE and adjust valves accordingly for Piston # 6.

You are now complete and can be sure everything is adjusted correctly. I am aware of how the Haynes manual as well as others have abbreviated this procedure and acknowledge it will work. The above procedure is the original way it was designed to be done and in my opinion leaves less room for error.