GM 91172318 Camshaft,Engine

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Disconnect the negative battery cable. Drain the engine oil and coolant. Remove the oil pan and the oil pump strainer. Remove the camshaft cover. Remove the timing chain cover. Remove the small timing chain, the chain tensioner, and the camshaft sprockets. Remove the Camshaft Position (CMP) sensor. Rotate the crankshaft 90 degrees in a clockwise direction. Loosen the camshaft bearing cap bolts in the indicated order. Note the location of the bearing cap studs. Remove the camshaft bearing caps and store them in order. Remove the dowel pin for the big camshaft bearing cap and store it in a plastic bag. Remove the camshafts. Note the offset slot in the end of the exhaust camshaft. Wipe off the top of each lash adjuster and clearly label it. Remove the lash adjusters and store them upside down in a pan of clean engine oil. Before installing the lash adjusters, squirt clean engine oil into the cylinder head oil passages. Squirt oil into the oil holes of the lash adjusters and verify that the oil comes out the holes in the friction surfaces of the lash adjusters. Install the lash adjusters in the cylinder head. Rotate the crankshaft sprocket counter-clockwise 90 degrees. Lubricate the friction and bearing surfaces of the camshafts with clean engine oil and then install the cams. Make sure that the pins on the cams are aligned with the match marks on the cylinder head. Install the dowel pin for the big camshaft bearing cap and apply sealant to the mating surface of that cap. Install the cam bearing caps in their correct locations. Lubricate the camshaft bearing cap bolts and studs with clean engine oil and then install them in their correct locations and tighten them by hand. Then, following the tightening sequence, tighten the camshaft bearing cap bolts gradually and evenly to the torque. Install the CMP sensor. Install the camshaft sprockets, the small timing chain, and the tensioner. Install the timing chain cover. Install the camshaft cover. Install the oil pump strainer and the oil pan. Refill the cooling system with coolant and the engine with oil. Start the engine and verify that there are no leaks. Check ignition timing and adjust as necessary.

Assessing cylinder head warping is essential during an engine overhaul because severe overheating can cause the cylinder head to warp. Warpage can affect the sealing of the head gasket and lead to coolant or compression leaks.