I have a lq4 6.0. I have prc heads with dual valve springs .660, Comp cam Hi-Tech 7.450" Long, .080" Wall, 5/16" Diameter Pushrods, comp cams hi-tech rocker arm studs 4554, comp cams pushrod guide plates 4854, comp cams rocker arm adjusting polylock nuts 4654, 1.75 rocker arms, and a XFI Xtreme Energy-R 224/230 Hydraulic Roller Cam. What I need to know is the correct valve lash/preload so I can adjust the polylocks. I got all these parts from a spare motor that ran great just putting them on a different motor.

 

Need the lifters make/model to know the preload.

 

it would be stock 2000 gmc 2500 6.0 lifters.

 

I’d set the preload to .080-.100 with those lifters. Polylocks makes everything much more difficult on a valvetrain that’s designed to be non-adjustable. You can get your rocker geometry out in left field quickly if you aren’t careful. The rocker arm should be at a direct 90 degree angle to the valve stem at mid-lift.