GMC 12693909 ARM ASM-VLV RKR

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But before you can take out the valve cover, all the valve adjusting lock nuts and screws must be unscrewed up to a certain point. Remove the rocker shaft mounting bolts and nuts gradually, and in an order that is opposite to the one used when tightening, till the amount of spring force is minimal. Raise the rocker arms and the shaft all together without the use of the shaft mounting bolt so that their relationship remains intact. If one wants to take a closer look at the assembly of the rocker arms or inspect them further, then he will have to remove the mounting bolts and slide the rocker arm and springs off the shafts but this must be done carefully in a manner that would enable one to have all the parts back in their former locations the next time around. Rocker arms for each cylinder should preferably be united and covered with a thick rubber belt. Wash and scavenge the parts well and look for wear and signs of damage especially on the tips of the rocker arms that touch the camshaft, the tips and the surface of the shafts which is normally badly scored and worn badly. Replace the worn out segment and it is important that the oil holes of the shafts are not blocked. Inspect the roller tips to ascertain whether or not they are worn out as well as their ease of operation. Take out the lost motion assemblies from the cylinder head and make sure they can slide well; clean them as well, as you check the plungers. Check the freedom of movement of the Rocker Arm Hydraulic Actuator pistons of each intake rocker arm. All the components should be lubricated with the engine oil before reassembling the shafts in their right positions as indicated on the upper and lower shafts and end with the rocker arms, shafts and springs which are right and left side ones. Apply camshaft installation lubricant to the wear surfaces of the rocker arms and then fit the rocker arm in position. Slowly and progressively, tighten the rocker shaft mounting bolts in accordance to the certain pattern to the called up torque. The rest of the removal process is done in the backward sequence to the installation process. After setting the valve clearances, operate the engine, and examine the engine for oil leaks and its proper functioning or not.

Once the rocker arms are removed, the hydraulic lifters can be lifted from the cylinder head.

Ensure the hole at the pushrod end of each rocker arm is clear and inspect the pushrods for cracks and excessive wear, confirming that the oil hole is not clogged.

Next, remove the valve cover(s).

Change the oil and install a new oil filter.

Apply moly-base grease to the ends of the valve stems and the upper ends of the pushrods.

Position the rocker arms onto the lash adjusters, and complete the installation by reversing the removal steps.

Each rocker arm should be checked for wear, cracks, and other damage, especially where the valve stems contact the rocker arm. The rollers should also be checked for binding and roughness.

Beginning at the drivebelt end of one cylinder head, remove the rocker arm mounting bolts one at a time and detach the rocker arms, pivot balls, and pedestals.

Before starting the engine, change the oil and install a new oil filter.