Chevrolet 12626407 Tensioner Kit, Timing Chain

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It is necessary to employ a special tool, camshaft holding tool, number GM# J-44221 or equivalent, for this operation. The timing system is a bit complicated and if a mistake is made during this process enormous damage to the engine can occur; therefore the work of this kind should be entrusted only to experienced personnel and it is mandatory to make sure twice of what has been done before starting the engine. Starting from TDC of cylinder number one the valve cover and the engine front cover should be unbolted; the word Delphi on the exhaust camshaft should be aligned with the valve cover mounting surface. Second, then, take off both the intake and the exhaust camshaft position sensors, then, the timing chain tensioner will then collapse thus requiring you to put a drill bit or a golf tee into position to keep it like that. Place the camshaft holding tool at the rear of the camshafts and then remove the top chain guide and the exhaust camshaft position actuator though holding the camshaft at the same time while undoing the bolt. Continue with the process of taking off the intake camshaft sprocket, disconnect the crankshaft sprocket from the camshaft chain, and then also take off the chain doing it while keeping the camshaft in a fixed position. Take out two access hole plugs from the front of the cylinder head, timing chain tensioner shoe bolt, timing chain guide bolt, after that take out the guide and shoe and the tensioner if they are being replaced. Take off the crankshaft sprocket, and prior to the startup of the engine, do the rotation of the crankshaft at least around two times and feel for any kind of load that signify an issue. When fitting the camshaft sprockets, fit new bolts and if disconnected, refit the tensioner and tighten to the indicated torque. Place the chain guide and shoe on the chain and tighten the bolts then fit the two holes with the access plugs. Before starting the engine, make sure that cylinder no.1 is again at TDC with the lobes of both Camshafts located at the front side of the Engine Head pointing upward with the Camshaft flats located at the back side also pointing upward. Fit the crank sprocket, still position the chain on the intake sprocket with one mark lined up with a dark link, thread the chain around the cylinder head through the crank sprocket ensuring the second mark is lined up. Bolt in the intake sprocket on the intake camshaft, and there might be a need to loosen and re-tightening of a holding tool for accurate alignment. Raise the timing chain up and manoeuvre the exhaust camshaft actuator over the correct sprocket so that a mark on the actuator is lined up with a dark link, then secure the actuator to the exhaust camshaft but do not over-tighten the bolt yet. Turn the exhaust camshaft actuator clockwise as far as it can be turned and make sure that the pointer is at the '0' mark before tightening the bolt. Loosen the intake camshaft sprocket bolt if it hasn't been done already and then use the drill bit or tee to turn the tensioner in and out Remove the camshaft holding tool. Lastly, align the timing mark and to finish the installation, reverse the whole procedure of removing number 4 cylinder head.

Begin by positioning the engine at Top Dead Center for cylinder number one.

Install the two access plugs and tighten them.