GM 10166352 Chain Assembly, Timing

To remove the timing chain cover, slide the shim off the nose of the crankshaft, ensuring the shim's notch fits over the key in the crankshaft. Replace the timing chain if the total free play between the sprockets exceeds one inch to avoid erratic engine performance, loss of power, and reduced fuel mileage. Temporarily install the vibration damper bolt and turn the crankshaft clockwise to align the timing marks on the crankshaft and camshaft sprockets directly opposite each other, with the camshaft sprocket marked by a dimple and the crankshaft sprocket by a raised dot. Remove the timing chain damper, detaching the spring on earlier models if necessary, and then remove the camshaft sprocket bolts, taking care not to turn the camshaft. Pull the camshaft sprocket and crankshaft sprocket forward alternately to remove them along with the timing chain as an assembly, followed by the camshaft gear. Clean the timing chain components with solvent and dry them with compressed air while wearing eye protection, then inspect for wear and damage, looking for deformed, chipped, pitted, polished, or discolored teeth. If the crankshaft has been disturbed, temporarily install the sprocket and turn the crankshaft until the mark on the crankshaft sprocket is at the top; if the camshaft was disturbed, do the same for the camshaft until its timing mark is at the bottom. Assemble the timing chain on the sprockets and slide the sprocket and chain assembly onto the shafts with the timing marks aligned, ensuring the balance shaft gears are also aligned before installing the camshaft timing chain sprocket. Install and tighten the camshaft sprocket bolt(s) to the specified torque, attach the timing chain damper assembly to the block, and install the spring. For 1994 and earlier models, install the camshaft thrust button and spring, securing it with grease. Lubricate the chain and sprocket with clean engine oil and install the timing chain cover, remembering to lubricate the oil pump cavity beforehand.

In models prior to 1990 the timing gears are used while in models from 1991 on the hydraulic tensioner, timing chain and sprockets are used. The timing gears on 1990 and earlier models cannot be accessed or replaced while the car is intact, but those of the 1991 and later models can by means of their timing chain/sprockets. To reach the timing cover, one needs to first remove the crankshaft pulley, then to unbolt the timing gear cover with 6 bolts and clean the sealing faces with a scraper and a degreaser. If necessary, remove the front oil seal by gently wedging it out and fitting a new one with the sprung belly towards the inside, using a sealer inserting tool or a considerable socket and hammer. RTV sealant should be applied across the mating areas of the front cover and oil pan and then the cover should be placed over the dowel pins, the crankshaft pulley, and the cover should be fastened with bolts, and they all should be tightened in a diagonal manner in equal intervals. Last but not the least, fit the crankshaft pulley back again into its place. On 1991 and 1992 models the timing chain should be checked for wear, and it should be replaced if the engine has high mileages, if it shows signs of damage or if there is excessive movement. Where possible, look at the sprockets and look at the tensioner for the timing chain and replace also if damaged. To take out the timing chain and sprockets one should turn the camshaft bolt, then set the timing marks at Top Dead Centre, and then take out the camshaft sprocket bolt without rotating the camshaft. Remove the timing chain and sprocket assembly carefully and always replace the timing chain and sprocket as a set and the key should be in position. Wash the parts with some solvent then dry the components using a puff of compressed air while maintaining eye irritation. Reassembly is done in the reverse of disassembly, and every fastener has got to be tightened to the prescribed torque values and the chain and sprockets have got to be coated with clean engine oil before having the timing chain cover put back on.

Verify the alignment of camshaft and crankshaft sprockets for correct valve timing.

Clean the timing chain, sprockets, and crankshaft oil slinger thoroughly in the appropriate solvent.

Recheck the positions of the camshaft and crankshaft sprockets for correct valve timing, ensuring the crankshaft is rotated appropriately to avoid damage.