FAQ: Scorpion Racing Products Lifters
What is the difference between hydraulic and mechanical lifters?
On the outside they look the same, inside is where the difference is. The mechanical (or solid lifter) is just what it sounds like, solid with no internal movement. These lifters are designed to be adjusted at lash (clearance) and are to be used on camshafts that are designed for a lash setting. Mechanical lifters require periodic adjustment and are normally used for higher rpm. However the advantages are they have no internal parts to stick or fail and the lash can be varied to help tune the combination. Hydraulic lifters are designed to run at no lash and have a moveable pushrod seat controlled by engine oil to accomplish this. They are normally adjusted to a "preload" (how far down from zero lash) setting and use a camshaft designed for a "no lash" situation. They are basicly a set and forget lifter because of the preload typeadjustment and are normally used up to approximately 6500 rpm.Hydraulic lifters (because of thehydraulic unit) are subject to bleed down issues caused by debris.
What are flat tappet and roller tappet lifters?
Flat tappets (lifters) have a flat face that rides against the cam lobe. In reality the face has a slight crown (convex) to help the lifter spin or rotate when the cam lobe moves past it. These are available in both hydraulic and mechanical. All Scorpion Racing Products flat tappets are made in the U.S.A. from a proprietary formula of hardenable cast iron for wear resistance. The face of the lifter has a high concentration of microscopic carbides and is mirror finished for durability in both street and high load race engines. Scorpion Racing Products mechanical flat lifters are available with and without a.015″ oil hole in the face. Scorpion Racing Products hydraulic flat lifters are available with three different types of hydraulic units, race, short travel and variable duration. Therace lifter has the travel and bleed rate of an "anti-pump up" race tappet, the short travel has .050 of hydraulic travel and a custom bleed rate for higher rpm. The variable duration lifter has a faster bleed rate to increase manifold vacuum and low speed performance. Flat lifters (hydraulic or mechanical) must be used with camshafts designed for that use. Roller lifters are noticeably different as there is a roller at the bottom that rides against the cam lobe and there is some means to stop the lifter itself from rotating in the lifter bore. These lifters are also available in either hydraulic or mechanical. All Scorpion Racing Products (hydraulic or mechanical) roller lifters are made in the U.S.A. from cold forged heat treated steel with a precision groundroller assembly using a tool steel axle. The hydraulic roller lifters are available in both "tie bar" and OEM style locking bar types. The tie bar style hydraulic roller is availablewith either race or with short travel hydraulic units. The OEM style are available with the race hydraulic unit only.The race hydraulic unit has the travel and bleed rate of a standard "anti-pump up" lifter while the short travel has .050 of hydraulic travel and a custom bleed rate for higher rpm. The Scorpion Racing Products mechanical roller tappets have a lightweight body with a proprietarytie bar design. They are available to fit taller lifter bore, hydraulic roller style engine blocks. Roller tappets must be used with roller lifter camshafts.
What is the best way to adjust my lifters?
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 changewhere the intake manifoldhasbeen 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 procedurecan beused on any engine with any camshaft. Remember to use Scorpion Racing Products assembly lube, SRPAL4-1, 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 engineto the correct postion (see "engine positon 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 tohave the feeler size you need for your adjustment and one that is .002 larger. Using thecorrect size to set your valve lash, then make surethe 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.