The most common reasons for using a pushrod that is longer or shorter than stock are: a decked cylinder block or heads, thicker/thinner head gaskets, small base-circle camshafts, aftermarket rocker arms, longer-length valves, valve jobs with varying seat depth, non-stock lifter designs and/or seat height, and converting to an adjustable valvetrain. These variables inevitably alter pushrod length; however, following these easy steps will help prevent improper geo-metry and ensure your engine's longevity.
Zero out the Comp Cams pushrod...
Zero out the Comp Cams pushrod length-checking tool, then install it in the lifter's pushrod seat and within the pushrod guide plate on the cylinder head (if applicable).
If your camshaft requires...
If your camshaft requires valve lash (our mechanical roller cam calls for 0.012 inch), insert the proper feeler gauge between the rocker-arm tip and the valve tip.
If the rocker-arm tip is beyond...
If the rocker-arm tip is beyond the 11/43-forward position, you need to return the lifter to the cam base circle, shorten the adjustable pushrod, and slightly loosen/tighten the rocker-arm adjustment nut (changing the initial 11/43-forward position). Next, readjust the checking-tool length so that it achieves zero lash on the backside of the rocker arm. Then roate the engine through its firing in order to note movement range of the rocker-arm tip.
While holding up the pushrod...
While holding up the pushrod end of the rocker arm, turn the rocker adjustment nut so that the rocker-arm tip is approximately at the 11/43-back position on the valve step tip. Note: the more you tighten the rocker adjustment nut, the further it moves the rocker-arm tip toward the 11/43-back position.
Rotate the engine through...
Rotate the engine through its firing order to open the valve as cam lobe increases. Stop when the cam lobe is at maximum lift. As the lobe lift increases, the rocker arm should move toward the opposite side of the valve tip (the 11/43-forward position).
Note how many turns out from...
Note how many turns out from zero the tool is. For each 360-degree rotation of the threaded end (adjustment amount indicated by thin white lines), add 0.050 inch to the measurement. For example, this checker tool (PN 7994-16) has a 7.80-inch length when zeroed out. To that we added three turns out (0.050 inch x 3) from zero, which brought us o a final length of 7.950 inches.