Tool required for this procedure is the special camshaft holding tool (part GM# J-44221 or equivalent). Start by rotating the crankshaft to set the engine to Top Dead Centre for cylinder number one, then unscrew the valve cover and the engine front cover. After collapsing the timing chain tensioner insert something like a drill bit or golf tee into the hole to keep the tensioner collapsed. The top chain guide can be removed by dismantling two bolts; next is the exhaust camshaft position actuator held by an Allen screw into a hex shape molded at the cam shaft while holding the camshaft still using a wrench. Then, take off the intake camshaft sprocket, relieve tension to the crankshaft sprocket and take off the chain while still holding the camshaft. Disconnect the two access hole plugs with a hex bit and the timing chain tensioner shoe bolt and the timing chain guide bolt, to pull out the guide and shoe and the tensioner, in case it is being replaced. The next step is to take out the crankshaft sprocket as is mentioned in the picture below. In case of his removal, the tensioner must be replaced and tightened to the optimum torque; the chain guide and the shoe must also be tightened with the bolts to the required torque. Screw in the two access plugs. Make sure cylinder one is still at Top Dead Centre, fit the camshaft holding tool making sure the lobes at the front of each camshaft are upright, the rear flats are upright. Insert crank sprocket and the chain must be fitted at angle on the intake sprocket on the marked dark link. Thread the chain over the cylinder head and over the crankshaft sprocket with the mark on the crankshaft sprocket lined up with a dark coloured link. Place the intake sprocket on the intake camshaft and it might become necessary to release a holding tool so as to slightly generate movement in the camshaft in other to align it before reengaging the holding tool. Raise the timing chain up and properly position the exhaust camshaft actuator over it; be sure that the mark on the absorber sprocket is over a dark coloured link before you install it to the exhaust camshaft permanently without heavily tightening the bolt. Once more, it can be just as necessary to wiggle the camshaft for proper positioning prior to reinstalling the holding tool. Turn the exhaust camshaft actuator clockwise until it cannot be turned further and set it in the position where the exhaust camshaft is fully advanced as failure to do this may cause severe problems to the engine. Retorque the intake camshaft sprocket bolt, respectively remove the drill bit or tee from the tensioner and withdrawal the camshaft holding tool. Last of all the timing mark should be aligned with the position where there are darkened links on the front of the intake camshaft sprocket, on the exhaust camshaft actuator and crank sprocket, then put all the parts back in as was done while removing them.
