I used a dial indicator on the tip of the rocker by the pushrod and tightened the rocker stands until the pushrod had zero preload. The cam was on the base circle, of coarse. I tightened the bolts till the shaft was tight to the stands and then read the indicator. Comp had a different way in some instruction I had once. They said to mark the pushrod at zero preload and and then tighten the shafts and mark again. Measure the difference and you have your preload. Both methods came out the same, .110.