If you do exactly the steps I outlined, you’ll end up with the correct length pushrods.
Those instructions are for a solid cam, which is where the use of the feeler gauge comes into play.
These instructions are only for shaft mounted rockers with cup style adjusters, that oil through the adjuster, that cannot be screwed “through” the rocker arm....... all of this is applicable to the Comp 1621-16.
**The old “number of threads showing under the rocker” technique does not apply to these rockers**
There is an oil band on the adjuster screw that must line up with the oil feed hole in the rocker body.
The range of adjustment for that to happen is a nominal zero turns out.......to......two turns out.
One turn from seated is the mid point.
On these rockers, the adjuster screw is installed from the bottom:
View attachment 1156013
Screw it in all the way till it stops:
View attachment 1156014
Screw it back down one full turn, install lock nut, snug it down:
View attachment 1156015
Install rocker on shaft, snug shaft down on head.
With cam on base circle(lifter as low as it can go), and checking pushrod in place...... adjust the length of pushrod/tool to eliminate all slack in the valvetrain.
If it’s a solid cam, have the correct thickness feeler gauge between the roller and the valve tip(the same thickness as what you use to set the valve lash).
**if you don’t use the checking spring, when the checking tool reaches the correct length, it will be hard to extend it any farther.
With checking springs, extending it too far will just start to open the valve.
I prefer to use the regular spring for the more positive feel when you’ve eliminated all the slack**
Remove the rocker from head, remove checking tool(being careful not to upset the adjusted length).
Measure tool. That’s the length of pushrods needed.
That’s all there is to it.
View attachment 1156050