Posted on May 13, 2020 C15 and C18 – Variable Valve Actuators – Inspect/Adjust Illustration 1 g01102463 (1) Adjustment screw (2) Adjustment screw locknut (3) Intake rocker arm (4) Actuator rod Put the No. 1 piston at the top center position on the compression stroke. Refer to Testing and Adjusting, “Finding Top Center Position for No. 1 Piston”. Loosen adjustment screw locknut (2) and back out adjustment screw (1) until actuator rod (4) is not in contact with intake rocker arm (3) . Note: During this procedure, ensure that the intake rocker arm is in full contact with the valve bridge. Place the appropriate feeler gauge between the actuator rod and the intake rocker arm. Turn the adjustment screw in a clockwise direction. Slide the feeler gauge between the actuator rod and the intake rocker arm. Continue turning the adjustment screw until a slight drag is felt on the feeler gauge. Remove the feeler gauge. Set the clearance to 0.50 ± 0.08 mm (0.020 ± 0.003 inch). Tighten the adjustment screw locknut to 50 ± 10 N·m (37 ± 7 lb ft). Recheck the lash setting after the adjustment screw locknut has been torqued. Make the lash setting on the following cylinders: 1, 2 and 4. Remove the timing bolt from the flywheel. Turn the crankshaft clockwise by 360 degrees. This will position the No. 6 piston at the top center on the compression stroke. Install the timing bolt in the flywheel. Repeat Step 6 for the following cylinders: 3, 5 and 6. Remove the timing bolt from the flywheel.