COMP Cams Camshaft Installation and Degreeing Procedure - Manual (Page 6)

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COMP Cams®
3406 Democrat Rd.
Memphis, TN 38118
Phone: (901) 795-2400 Fax: (901) 366-1807
www.compcams.com
Part #145
Revised 5/4/12
Non-Adjustable Rocker Arms: A different procedure is required to set hydraulic lifter pre-load on
engines with nonadjustable rocker arms. After applying lube, install the pushrods and torque all rocker
arm bolts down in the proper sequence and torque specification. Rotate the engine by hand in the
normal direction of engine rotation until both the exhaust and intake valves have opened and closed
completely. Allow a couple of minutes for the lifters to bleed down.
Using the valve cover gasket surface on the head as a reference point, place a mark on the pushrod.
The smaller more defined the mark, the more accurate the measurement. Be sure the reference point
you choose for the first mark is easily accessible and easy to duplicate. The pushrod will be marked
twice. It must be from the same reference point and angle for the measurement to be accurate.
Loosen the rocker or rocker shaft bolts. Leave the rockers on the head so that they will support the
pushrods. Be sure the pushrods are standing free in the lifters, and do not have any pre-load. Using the
same reference point, place a second mark on the pushrod. Make sure the angle and reference point are
the same as the first mark.
You now have two marks on the pushrod; one with the assembly bolted into place as the engine will
run, and the second mark with the lifter unloaded. The distance between these two points will represent
the amount of lifter pre-load. If the pre-load is not within .020” to .040,” adjustment is necessary. The
simplest way to accomplish this is by using different length pushrods. When measuring to find the
correct length needed, be sure to include .030” pre-load that the lifter requires. If the engine uses
pedestal mount rockers, shims can be placed under the pedestal to reduce the pre-load. The stands on
shaft mounted rockers can also be shimmed in this manner. Longer pushrods will be needed for
insufficient pre-load.
In most cases, only one intake and one exhaust pushrod will need to be checked. If the valve stem
heights are not equal, then pre-load will have to be checked on each valve. If you do need custom
length pushrods, call CAM HELP at 1-800-999-0853. COMP Cams offers a variety of pushrods in
most lengths.
Rocker Arm Clearance
Rocker arm clearance must be checked at several places. It is very common with higher lift cams to
have the rocker arm contact the rocker stud when the valve is in the full open position. Be certain to
check this, as lack of proper clearance will cause broken studs, broken pushrods or a worn-out
camshaft.
The clearance between the rocker arm and the valve spring retainer must also be checked. This
problem will be more pronounced when the valve is closed. The retainer is most likely to contact the
underside of the rocker arm right in the center. Be sure to maintain at least .030” clearance at this
point. Pushrod clearance must also be checked, especially when using higher ratio rocker arms. The
pushrod seat in the rocker is moved toward the stud in this case, so it must be checked at several
different lift points for contact with the cylinder head or guide plate.