The first step in the preload setting procedure, for which ever valve you’re working on, is to back the adjuster off far enough to allow the lifter plunger to completely top out against the retaining clip........ plus a little more so there is definite vertical free play between the rocker/pushrod/lifter.
Then, before taking out the free play, make sure the pushrod is properly seated in the pushrod cup of the lifter.
Since on a SBM the lifters are somewhat “laying on their side”, it’s not hard to end up with the pushrod sitting on the top edge of the pushrod cup, instead of down in the cup.
Turn the adjuster screw in while jiggling the pushrod vertically until you notice you have “just” eliminated all the free play.
Then you add in the lifter preload(1/2 turn, etc).
After doing this, some lifters will be “soft”, some will be “hard”.
That’s normal.
The Comp 20-228-4 is one of the XE/HL series of cams.
It’s unlikely you will ever get the valvetrain to be truly “quiet” with that cam.
Take your time on the lifter preload adjustment so you’re confident in the setting........ then the noise situation just is what it is.
