Proper valve adjustment is crucial to the performance and longevity of any engine, but for this tech tip we will concentrate on valve adjustment for a performance engine equipped with a larger (higher duration and lift) than stock performance camshaft.
First let’s define a couple common terms we need to know. First is preload, which is the amount we have preloaded the lifter in either a hydraulic flat tappet or hydraulic roller camshaft and lifter setup. The second is lash which is the amount of gap, or lash, between the tip of the rocker arm and the valve stem in a solid or mechanical flat tappet or roller camshaft and lifter setup.
Adjusting the valves on either a hydraulic or solid camshaft/lifter is the same procedure, as far as when we perform the adjustment procedure.
You may want to perform the adjustment procedure in the engines firing order, starting with the number 1 cylinders intake valve then its exhaust valve and then moving on to the next cylinder in the firing order but it isn’t completely necessary as long as you perform the procedure on each individual cylinder the same way.
The Intake valve will be adjusted when the exhaust valve of the same cylinder is just starting to open and you will adjust the exhaust valve when the intake valve is just starting to close.
To perform the procedure rotate the engine by hand, as soon as you see the exhaust valve begin to open adjust the intake valve. Once adjusted continue to rotate the engine until the intake valve opens entirely and just begins to close, now adjust your exhaust valve. That cylinder is now complete.
Adjusting valves on a hydraulic camshaft. Once the valve is in position following the above procedure turn the adjusting nut until there is zero lash between the push rod and the rocker arm, turn the adjusting nut ½ to ¾ of a turn. You have now put adequate preload into the hydraulic lifter.
Adjusting valves on a solid/mechanical camshaft. Once the valve is in position following the above procedure, place the appropriate feeler gauge between the valve stem and the tip of the rocker arm, tighten adjusting nut a little at a time until a slight drag is felt while installing and removing feeler gauge.