GM 91177364
Valve Lifters

First disconnect the negative Battery Cable then remove the rocker-arm cover as the first step to start replacing the Lash Adjuster. The first step requires removing both the Timing Belt and Camshaft from the situation. Extract the six hydraulic lash adjusters that are inside the Cylinder Head. Engine oil installation requires a pouring step through Camshaft journal holes which must drain out from the Lash Adjuster bores oil holes. The Lash Adjuster needs engine oil applied for installation onto the Cylinder Head. Before placing the Cylinder Head Camshaft into position, apply engine oil to the Camshaft journal along with all cam surfaces and direct the Camshaft timing gear pin hole to remain in the lowest position. Apply gm p/n 12346240 or an equivalent to the mating surface of housing number 1 and number 3 facing the Cylinder Head while sliding engine oil on each component against the Camshaft journal. Fit housing number 1 to journal number 1 but leave it untightened before placing the housing assembly opposite the Timing Belt side of the Camshaft and Cylinder Head. The stored arrow on the housing should face the desired direction. The Camshaft housing bolts must receive a thin layer of engine oil before they are bolted onto the Camshaft journal. Secure the remaining two Camshaft housings (2 and 3) onto the Camshaft journals through housing bolts while progressively tightening them to 11 nm (97 inch lbs.) during three to four bolt-tightening sequences. Before complete insertion add engine oil to the outer edge of the Camshaft oil seal and push the seal until it aligns with the housing face. After applying oil to the mounting holes of the housing bolts, install the Camshaft while replacing the Timing Belt and reattaching the rocker-arm cover.

The beginning of exhaust camshaft and lifter replacement requires disconnecting the negative Battery Cable. First obtain the Timing Chain housing followed by removing the camshaft Timing Chain together with the exhaust camshaft sprocket. Record matchmarks on the position sensor and the Cylinder Head that will become visible after removing the sensor. After positioning the Crankshaft at 90 degrees to avoid valve-piston locking you should proceed to loosen and remove exhaust camshaft bearing caps starting with the initial one then move onto the exhaust camshaft itself. The valve lifters require placement in engine oil until installation while being situated camshaft-side down but disassembly and forcing between operations must be avoided. The combimike micrometer (J 26900-2) should be used to measure camshaft lobe height until replacement becomes required when any lobe falls below 39.721 mm (1.5638 inch). The dial indicator set (J 3001) and magnetic indicator base (J 26900-13) determine the camshaft runout. Replace the camshaft if runout measures greater than 0.10 mm (0.0039 inch). The assessment of camshaft bearing caps and journals for damage or wear marks should lead to Cylinder Head replacement if needed. Install the camshafts after cleaning them while ensuring the exhaust camshaft rear end faces the Camshaft Position Sensor. Use gaging plastic tools to measure oil clearance between 0.020 - 0.074 mm (0.0008 - 0.0029 inch). The combimike micrometer (J 26900-2) should measure the journal diameters when camshaft clearance surpasses the maximum reading. Check valve lifter dimensions for wear by measuring their clearance against the valve bore while ensuring it remains within normal specifications. First empty the valve lifter bore with engine oil before adding oil to the lifters while they return to their specific bores. Placing the Crankshaft keyway on the timing mark while applying oil to camshaft journals allows the correct installation of camshafts in proper alignment. Dowel pins should be installed before applying gm p/n 12346240 (Canadian P/N 1O953493) as a bead across the exhaust camshaft end housing. To properly install the Camshaft Position Sensor after aligning its matchmarks you should progressively tighten the bearing caps to 11 nm (97 inch lbs.). After installation the exhaust camshaft sprocket must be combined with the Timing Chain and Timing Chain housing while the valves should remain inactive for about thirty minutes to protect against equipment damage. Before reconnecting the negative Battery Cable check the ignition timing if needed.

Flush debris from the valve lifter bore with engine oil.