Rocker Arm Geometry - Rock Me Baby!

Checking Rocker Arm Geometry

Ray T. Bohacz Jul 1, 2004 0 Comment(s)
Sucp_0407_01_z Rocker_arm_geometry Valve_lift_checker 2/8

The first step is to determine the maximum valve lift generated by the camshaft and to record the value. To do this, you will need to fixture a dial indicator to the valve stem with either a bracket or magnetic stand. If you do not have these tools you can still check the rocker arm geometry by eye, but SUPER CHEVY does not recommend it.

One of the most common mistakes when building a Chevy engine is neglecting to check the rocker arm geometry. This is usually due to the name of the procedure being misleading and implying the application of higher math. What is required is to check the position of the rocker arm tip on the valve stem during the opening event. The procedure is quite simple and if an error is discovered, it is easily corrected.

Whenever the block or cylinder head deck is machined, the distance to the valve lifter will be altered and the push rod length will need to be modified to keep the geometric angle correct. Additional causes for error are a change in valve lifter style and height, the length of the valve stem, the installed height of the valve, the depth of the spring pocket in the cylinder head, and the design of the rocker arm.

Checking the rocker arm geometry should be a step whenever assembling an engine, even if standard stamped-steel rockers are used.

Follow along as SUPER CHEVY takes the mystery out of this procedure.


Racekrafters Auto Machine Inc.
Lancaster, PA 17601




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