GMC 12690246 Adjuster Assembly, Dual Feed Hyd Vlv Lash

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Removal involves removing the valve covers and the camshafts to remove the rockers is the lash adjuster socket on the rocker. Place markings on each rocker arm to ensure they are returned to the same position, then lift each one from the engine. Once the rocker arms are removed, the hydraulic lash adjusters can be lifted from the cylinder head. It is important that any rocker arms or lash adjusters being used again must be returned to their original position on the engine. Inspection involves checking each rocker arm for wear, cracks and other damage, especially where the valve stems contact the rocker arm. Check the rollers for binding and roughness. If the bearings are worn or damaged, replacement of the entire rocker arm will be necessary. Keep in mind that there is no valve adjustment on these engines, so excessive wear or damage in the valve train can easily result in excessive valve clearance, which in tum will cause valve noise when the engine is running. Make sure the oil passage hole in each hydraulic lash adjuster is not blocked. Installation involves applying some camshaft/lifter prelu be to the pivot pockets, roller and the slot that contacts the valve on each rocker arm. Apply clean engine oil into the bores for the hydraulic lash adjusters and install them into the cylinder head. Position the rocker arms onto the lash adjusters. The remainder of installation is the reverse of removal. Before starting and running the engine, change the oil and install a new oil filter.