GM 91174417
Camshaft Gear

Start by disconnecting the negative Battery Cable then remove the timing chain housing before beginning the replacement of the Camshaft timing chain and sprockets. Remove spark plugs first to help turn the Crankshaft for proper timing mark position before disassembly because this prevents damage to valves and pistons. Engine block marks allow users to align crankshafts 90 degrees and Cylinder Head notches enable turning camshafts 15 degrees when needed. To achieve correct alignment rotate the Crankshaft until the number 1 cylinder reaches top dead center (TDC) as the Crankshaft keyway faces the engine block mark while the idler sprocket arrow points up with the Camshaft guide pins located at the Cylinder Head. You should start by turning the intake Camshaft counterclockwise until the tension eases then remove the retaining nut together with bolts 1 and 2. The Camshaft Timing Chain Tensioner and gasket follow next. With a wrench secure the Camshaft before removing its sprocket bolts so you can remove the chain along with the sprockets. Carefully check the Camshaft timing chain upper guide and tensioner together with tensioner gasket and sprockets and chain components for wear indicators and damage. Replace all components showing wear or damage. During installation position the Crankshaft keyway exactly at the engine block mark while the idler sprocket arrow faces up and the Camshaft guide pins must align with notches on the Cylinder Head. The installation requires the yellow Camshaft timing chain link to match the arrow on the idler sprocket combined with the dark blue link that aligns with arrows (2,3) on the Camshaft sprockets. When installing the Camshaft sprockets with their attached chain, torque all Camshaft sprocket bolts to 80 nm (58 ft. Lbs.). Compress the Camshaft tensioner plunger into the body and lock it with the retainer, next position the gasket and Camshaft Timing Chain Tensioner in place before tightening bolts to 11 nm (97 inch lbs.) and the nut to 45 nm (33 ft. Lbs.). Turn the Crankshaft two times to match the keyway position on the Crankshaft with the engine block timing mark. At this point check that the Camshaft guide pins sit properly within their notches on the Cylinder Head. First apply engine oil to the timing chains with their components and tensioner and guides and sprockets before you put the spark plugs in with a 25 nm (18 ft. Lbs.) tightness. Install the timing chain housing while reconnecting the negative Battery Cable as the last step.

To replace the timing chain and sprockets on the Crankshaft, one is required to remove the negative Battery Cable and the sparkplugs to allow one to aid in the function of clocking the Crankshaft. Remove the timing chain housing taking note of the correct timing of its marks before disassembling it. The camshafts can be rotated 15 degrees off the notches on the Cylinder Head (15 degrees), but in case it is needed, the Crankshaft can be rotated 90 degrees off the mark on the block of the engine (15 degrees). Rotate the Crankshaft and make it align with the number one cylinder at top dead centre, key on Crankshaft face with mark from engine block, idler sprocket with arrow pointing upward, camshaft sprockets should be guide pins aligning to the notches on the Cylinder Head. Relieve tension on the Camshaft timing by turning the intake Camshaft a little counter clock wise, remove the nut and 2 bolts (1,2) do not turn the Camshaft or Crankshaft after and remove the tensioner. Take out the Camshaft Timing Chain Tensioner and gasket, use wrench to get the cam shaft, take out the Camshaft sprockets and chain before removing the Camshaft sprockets and chain bolts. Inspect the Camshaft timing chain upper guide, tensioner, tensioner gasket, sprockets, and chain for wear and damage, replacing any parts that have worn out. Secondly, unscrew the 2 bolts and Crankshaft Timing Chain Tensioner, the bolt and Crankshaft timing chain adjustable guide, and the 2 bolts and Crankshaft timing chain fixed guide. Take out the idler sprocket and Crankshaft timing chain, followed by its Crankshaft timing sprocket, the latch in the timing chain guides, idler sprocket, crankshaft timing sprocket, and Crankshaft timing chain for wear and damage while replacing worn parts ensuring the latch and teeth of your Crankshaft Timing Chain Tensioner work correctly before replacing them. For installation, make sure the timing mark of engine block corresponds to the Crankshaft sprocket keyway, then install Crankshaft sprocket and apply engine oil on idler sprocket bushing. Swing the timing chain across to the idler sprocket, locate the mark on the sprocket and the dark blue link , then push the link onto the mark. Swing the timing chain across to the Crankshaft sprocket locating the mark on the Crankshaft sprocket and the yellow link then push the link onto the mark. Install the idler sprocket and the timing chain fixed guide with the bolts tightened to 9 nm (62 inch lbs.) and the timing chain adjustable guide with bolt tightened to 25 nm (19 ft. Lbs.). Push back the latch, compress the plunger and retain the plunger with a retainer before you will install the Timing Chain Tensioner using bolts with a torque setting of 11n.m (97 inch lbs.). Remove the retainer and ensure the Crankshaft keyway aligns with the mark on the engine block , the yellow link of the Crankshaft timing chain aligns with the Crankshaft timing mark , and the dark blue link aligns with the mark on the idler sprocket. Make sure the guide pins of the camshafts to align with the notches of the Cylinder Head, and the idler sprocket arrow should be pointing upwards. Compare the alignment of the yellow link of the Camshaft timing chain with the arrow on the idler sprocket and the dark blue link with the arrows 2,3 on the Camshaft sprockets before installing the Camshaft timing sprockets and chain before the Camshaft sprocket bolts are tightened to 80 nm (58 ft. Lbs.). Push in the Camshaft on the plunger into the body and secure it with retainer to keep still fit Camshaft Timing Chain Tensioner by applying bolts that are screwed to the tensioner 11 nm (97 inch lbs.) and nut 45 nm (33 ft. Lbs.). Take off the retainer, turn the Crankshaft 2 revolutions for realigning the keyway, the Crankshaft with the timing mark, engine block , and that guide pins on camshafts are in line with notches on Cylinder Head . Apply engine oil to the timing chains, tensioner, guides, and sprockets, install the spark plugs, set tightness to 25 nm and 18 ft. Lbswu of torque, then install the timing chain housing, and reconnect the negative Battery Cable.

Turn the intake camshaft slightly counterclockwise, then remove the nut and bolts, followed by the camshaft timing chain tensioner and gasket.