6. To check and adjust the lifter preload, turn the bolt by hand until
there is no clearance between the front roller and the valve stem
and the pushrod is seated in the rocker arm pushrod seat. Slowly
torque the bolt to 18-20 ft/lbs. Since you are pushing down the
plunger in the hydraulic lifter as you torque the bolt, it will probably
take a minute or two for you to get the correct setting. You
should be able to turn the bolt between 1/4 & 1 turn before you
reach the correct torque setting. This will give you the correct lifter
preload of .020" to .060". If you can turn the bolt more than one
turn to achieve the proper torque, you will have to shim the
pedestal. Two different thickness shims are provided for each
rocker arm to assist you. A thick shim represents approximately
one turn.
If you cannot turn the bolt at least 1/4 turn after first contact with
the roller and valve stem, you will have to install longer pushrods
to obtain proper hydraulic lifter preload. Pushrods are available in
different lengths, specifically for this purpose. There are many
modifications that may have been made to the engine which will
change the lifter preload, such as a valve job, different camshaft,
or different thickness head gaskets, and factory tolerances can
also affect the lifter preload on stock engines.