ROCKER ARM ADJUSTMENT AND LIFTER PRELOAD
Many engines and all but a few Chrysler engines were equipped at the factory with non-adjustable rocker arms. Anytime a solid lifter roller or flat tappet camshaft is used, you must also use adjustable rocker arms and the appropriate pushrods. When installing any high-performance hydraulic camshaft, the lifter preload is something which must be considered. Too little preload will result in a noisy valve train, and too much preload will result in tight valves and a poor running engine. The result is less than expected performance and/or engine failure with either condition. Once the cam, lifters and rocker arms are installed, and prior to installing the intake manifold, you must check the plunger depression in the lifter. With the cam on the base circle (valve closed) the plunger in the lifter should be depressed .040″-.060″. With nonadjustable rocker arms, you must change pushrod lengths to obtain proper lifter preload. This can be a delicate and time-consuming process but is absolutely necessary.
Engine Pro Technical Committee with special thanks to the Edelbrock Group and Comp Cams
NOV, 2022
