A special camshaft holding tool Number GM# J-44221 or equivalent is necessary for this action. When the cam sprocket has been taken off, do not turn the crankshaft this may cause improper timing of the engine with consequent damages of the engine. Start by unwiring the valve cover and the spark plugs so as to be in a position to rotate the engine. Turn the engine clockwise until grooves for sprockets match with a black link on the chain; the flats at the back of the camshafts will be up if the engine is at the Top Dead Centre for cylinder number one. Take out the camshaft sprocket bolts, and then do so carefully with the sprockets of the camshafts. Make sure the camshaft caps have been scribed; if they haven't been scribed, scribe them with paint before you remove them, so that it will be easier for you to align them later. Loosen and take out the camshaft cap bolts and in slow procedures extract the camshafts with caution to ensure that each of them is not mixed up. This is a good time to lift out the rocker arms and the lash adjusters and it will be wise to ensure that set is orderly set aside to be re-fixed later. When camshafts are removed they should be cleaned with solvent and dried, Check each camshaft for; scored journals, heat discoloration, score marks, chipped areas, pitting and uneven wear, damaged sprocket locator slots and damaged threads. You can use micrometer to take measurement of bearing journals looking for elevated levels of wear or out-of-round. To replace it, the lash adjusters and rocker arms must be immersed in clean engine oil, before being placed back in their positions. Ensure that the camshaft is clean then apply some drop of clean engine oil on the camshaft before putting it on the right place on the cylinder head and then fitting the holding tool for the camshaft correctly. Replace all camshaft caps in their proper positions and tighten them using your hands, afterwards using a pattern tighten the caps to the prescribed torque. Take out the holding fixture, put the sprockets on the camshafts in the right way, and screw the bolts to the suggested level of tension. However, after removing the crankshaft pulley bolt, positioned with large breaker bar and socket on it, rotate the crankshaft 720 degrees the crankshaft twice and again examine the sprocket and chain and see to it that the darkened links lines up with the sprocket marks. Any kind of grinding or any feeling of friction when working on the crankshaft should indicate that operations have to be ceased. Finally, fit back the spark plugs and the valve cover in position.
