GM 12556298
Rocker Arms

The replacement of valve Rocker Arm and push rods requires proper marking and organization of Cylinder Head components to achieve their correct position during reassembly. The first step includes removal of the valve Rocker Arm cover followed by valve Rocker Arm nuts and balls and finally removing the valve rocker arms. When removing valve pushrods you must do it according to the length difference where the exhaust valve pushrods exceed the intake valve pushrods. After removing valve Rocker Arm studs together with Pushrod guides you must clean the valve rocker arms and pushrods for inspection. When installing the system apply gm p/n 12346004 (Canadian P/N 10953480) sealant onto the valve Rocker Arm stud-to-Cylinder Head threads before inserting Pushrod guides and valve Rocker Arm studs and torquing them to 50 nm (37 ft. Lbs.). Keep in mind to use the correct position for the longer exhaust valve pushrods during installation. Use gm p/n 12345501 lubricating (Canadian P/N 992704) to coat valve Rocker Arm surfaces and valve Rocker Arm ball bearings before installing the valve rocker arms together with valve Rocker Arm balls and valve Rocker Arm nuts which require a slow-tightening to 25 nm (18 ft. Lbs.) while steering the rocker arms over the valves. Place and install the valve Rocker Arm cover as the final step.

After removing the Rocker Arm cover position all rocker arms pushrods and pivot support in a rack where their original positions can be preserved before starting the replacement process. Unbolt all Rocker Arm pieces then take off the rocker arms and Rocker Arm pivot support as well as the pushrods. Inspection of rocker arms and pushrods can be followed by cleaning procedures. After reinstallation all components must return to their original positions because valve lash emerges as an automatic result without requiring adjustments. A clean engine oil coating should be applied to both the Rocker Arm sections and pushrods followed by flange lubrication of the Rocker Arm bolt. Screw in the Rocker Arm pivot support while checking that pushrods drop into valve lifter sockets and manholes of the rocker arms yet refrain from bolting the Rocker Arm shafts. The Crankshaft should be rotated to reach its top dead center compression point with the number one Piston which sets the number one cylinder rocker arms beyond their lift range and positions the Crankshaft sprocket key at 1:30. Apply 30nm torque to all Rocker Arm bolts securing the cylinders 1, 2, 7 and 8 exhaust valves and the cylinders 1, 3, 4, 5 intake valves while the engine maintains its current position. Apply 30 nm torque to the Rocker Arm bolts of cylinders 3, 4, 5 and 6 exhaust valves after rotating the Crankshaft by 360 degrees and apply 30 nm torque to the bolts of cylinders 2, 6, 7 and 8 intake valves at this point. Rocker Arm cover must be installed at the end of the process.

Start the valve Rocker Arm and push rod exchange by taking off the Rocker Arm cover followed by placement of rocker arms pushrods and pivot support in a rack to keep their original configuration. Begin by removing bolts from rocker arms and then proceed to remove rocker arms and Rocker Arm pivot support as well as pushrods. You should perform cleaning and checking procedures on rocker arms along with pushrods. Engine oil lubrication should be applied to the rocker arms and pushrods before installation and the rock-arm bolt flanges must be treated with oil also. Place the Rocker Arm pivot support while verifying the proper position of pushrods inside valve lifter sockets and Rocker Arm ends without installing the Rocker Arm bolts at this time. Set the Crankshaft sprocket key at the 1:30 position when the number one piston reaches top dead center (TDC) of its compression stroke. You should apply 30 nm (22 ft. Lbs.) torque to the Rocker Arm bolts for exhaust valves of cylinders 1, 2, 7, 8 and for intake valves of cylinders 1, 3, 4, 5 while the engine is at this specified Crankshaft position. The Crankshaft must rotate a full circle so tighten exhaust Rocker Arm bolts of cylinders 3, 4, 5, 6 to 30 nm (22 ft. Lbs.) and the intake Rocker Arm bolts of cylinders 2, 6, 7, 8 to 30 nm (22 ft. Lbs.). The last step includes the installation of the Rocker Arm cover during the engine repair process.

The first step to replace valve rocker arms and push rods requires marking all Cylinder Head parts before sorting them properly to establish correct installation sequence. Commence the replacement process by taking off the valve Rocker Arm cover and proceeding to extract the valve Rocker Arm nuts along with valve Rocker Arm balls and finally removing the valve rocker arms. Pay attention since exhaust valve pushrods exceed the length of intake valve pushrods. The replacement process starts with removing valve pushrods then the valve Rocker Arm studs and Pushrod guides before cleaning and inspecting valve rocker arms and pushrods. You should treat the threads of the valve Rocker Arm stud-to-cylinder head with gm U.S. P/N 12346004, canada P/N 10953480 or equivalent sealant before using the Pushrod guides and valve Rocker Arm studs. The torque should be set at 50 nm (37 ft. Lbs.). Check that exhaust pushrods exceed intake pushrods in length before valve Pushrod installation. Apply gm u.s P/N 12345501, canada P/N 992704 or equivalent lubricant over the valve Rocker Arm along with its ball bearing surfaces before installing all components and gently tightening valve Rocker Arm nuts to 25 nm (18 ft-lbs) through valve guides. Installation of the valve Rocker Arm cover should be the last step in the assembly process.

The process of valve Rocker Arm and push rod replacement begins by removing the Rocker Arm cover followed by arranging the components on a rack because proper reassembly depends on this order. The replacement process begins by removing the Rocker Arm bolts and then proceeding to take out the rocker arms and Rocker Arm pivot support together with the pushrods. The cleaning process should be combined with an inspection of both rocker arms and pushrod components. Engine oil lubrication for both rocker arms and pushrods must occur before reinstallation while also applying oil to the flange section of the Rocker Arm bolts. Place the Rocker Arm pivot support while verifying pushrods fit the valve lifter sockets and then position the pushrods in the rocker arms before leaving the bolts untightened. Insert the rocker arms and bolts after manually rotating the Crankshaft to reach the top dead center compression stage when the number one Piston stands at that point while the sprocket key lines up with the 1:30 position mark. The procedure for this firing position involves applying torque to 30 nm (22 ft. Lbs.) for exhaust valve bolts on cylinders 1, 2, 7 and 8 and intake valve bolts on cylinders 1, 3, 4 and 5. Follow the Crankshaft rotation by 360 degrees until you tighten all Rocker Arm bolts. The exhaust valve bolts for 3, 4, 5, 6 cylinders require 30 nm (22 ft. Lbs.) torque while the intake valve bolts for 2, 6, 7, 8 cylinders need 30 nm (22 ft. Lbs.) torque. You should install the Rocker Arm cover as the last step.

Finally, install the valve rocker arm cover.

Remove the valve rocker arm cover, ensuring to store used components in order for reassembly.

The engine firing order is 1, 8, 7, 2, 6, 5, 4, 3, with cylinders 1, 3, 5, and 7 on the left bank.

Next, take off the valve rocker arm nut.

Coat the valve rocker arm and valve rocker arm ball bearing surfaces with lubricant GM P/N 12345501 (Canadian P/N 992704).