I am trying to set zero lash to check pre-load on my Comp R lifters w/ Yella Terra rockers. I can tighten the rocker arm bolt until the pushrod stops turning but when I lift on the valve stem side of the rocker arm the piston in the lifter compresses down about 1/4" - 3/8". Is zero lash the point where the pushrod is hard to turn or where the lifter piston is fully compressed? Any help would be appreciated.

 

Zero lash is with the lifter piston at the top (fully extended) and the pushrod just slightly hard to turn (no slack in anything). Preload is when you start to push the lifter piston down into the body of the lifter. Fully compressed is when you have maxed out the lifter and that’s a bad thing!

Yella Terras are not adjustable (other than spacers) so whatever the pushrod length is will determine you’re preload.