The easiest way to explain this is to take it in three sections; engine position to proper adjustment, hydraulic lifter adjustment and mechanical lifter adjustment. These instructions will work on flat or roller lifter engines. Also if this is a new engine or a cam change where the intake manifold has been removed, leave the manifold off when doing your initial adjustments as it is easier to watch the lifters while positioning the engine and for adjusting. To position the engine for proper adjustment you will work on one cylinder at a time and always turn the engine in the normal direction of rotation. This procedure can be used on any engine with any camshaft. Remember to use Scorpion Racing Products assembly lube, AL4-1, on all parts.
Engine position for adjustment: To adjust the intake lifter/rocker, rotate the engine and watch for the exhaust lifter to be on the low portion of the cam (valve closed) and continue rotating the engine until the exhaust lifter just starts to rise (valve just starting to open), stop and adjust the intake. To adjust the exhaust lifter/rocker, rotate the engine watching the intake lifter. The lifter will rise and then go back down, just as it stops moving down (valve just closes) stop and adjust the exhaust.
Hydraulic lifter adjustment: When adjusting hydraulic lifters, don’t installthe rocker until you’re ready to adjust it. When you have the engine in the correct position (see above) for adjustment, install the pushrod and rocker, tightening the adjusting nut with your fingers (make sure the locking set screw is backed out far enough on the adjusting nut). When the free play or lash (up and down movement) has been taken out of thevalve train (zero lash), use a wrench and turn the nut down (preload) the recommended amount. Then lock the set screw down against the rocker stud. Scorpion Racing Products recommends 1/2 to 1 turn down on all but our short travel. On our short travel lifters it’s 1/8 to 1/4 turns down. After reading this you now know that with the intake manifold off you can see when you’re at zero lash, because the free play is gonebut the pushrod seat is still up against the snap ring in the lifter. You can also see when you’re preloading because you can see the pushrod seat move away from the snap ring in the lifter. If it is a pedestal mount, non-adjustable rocker the procedure is basicly the same. With the engine in the proper position, install the rocker and lightly tighten the attaching screw with your fingers. Once you’re at zero lash, set your torque wrench to the specified torque and tighten the attaching screw. The screw should turn another 1/4 to 3/4 (1/8 to 1/4 turn with short travel lifter) turn until the torque wrench clicks. Ifitis less than 1/4 turn, a longer pushrod is needed. If it is more than 3/4 turn, a shorter pushrod or shimming the pedestal is needed.
Mechanical lifter adjustment: When adjusting mechanical lifters, rotate the engine to the correct position (see “engine position for adjustment” above), install the rocker arm and set the lash to the cam grinder’s specs. If you are not used to using a feeler gage, it would be best to have the feeler size you need for your adjustment and one that is .002 larger. Using the correct size to set your valve lash, then make sure the larger size doesn’t fit. This will stop you from having the lash too loose and will help you establish a “feel”. When adjusting the engine cold; on iron head/iron block use the recommended lash, on alum head/iron block, subtract.006 from the recommended lash, on alum head/alum block subtract .012 from the recommended lash setting. Then recheck lash with the engine at operating temperature. Remember for initial startup or cam break-in with mechanical tappets, tighter lash is better than too loose. Naturally you don’t want it so tight it will hold the valve open.