Ryunker,
you have a couple of specifications to look at here.
lifter preload is the specification used to determine how far the adjuster nut gets turned down when each rocker arm is adjusted from zero lash with the cam lobe from the rocker you are adjusting on the base (no lift ).
Then the rocker is turned down until all slack is taken up and you feel a slight drag on the pushrod while trying to spin it with 2 fingers.
Now you are at zero lash, from there one really needs to know what your lifter manufacturer recommends for preload. (preload is usually measured in thousands of an inch and will probably end up in the neighborhood of from 1/2 to one full turn.
one can use wrench flats as a guide, when you figure out how many thousants of an inch per flat.
the second specification would be how tight to tighten the set screw on the locks Don c describes to keep the first adjustment where it was adjusted to.
Sooo how much preload depends on whose lifters you are using.
not knowing your knowledge base, I would suggest visiting some web sites of lifter manufacturers
and reading install notes and watching a video or two.
My personal specs just happened to be 3/4 of a turn and set the lock screws to 20 lb.ft. torque.
Boilermaster
