Pontiac 12453171 Bearing, Camshaft

To measure camshaft lobe lift the first step is to remove the rocker arm covers to enable checking the number one piston at TDC on the compression stroke to determine wear. Slacken the rocker arm nuts on the number one cylinder valves and rotate the rocker arms to their highest position and fit a dial gauge pointer to the first push rod plunger so that it will bear on the top of the push rod at right angles to the centre line of the cylinder. Zero the dial indicator and slowly turn the crankshaft until the indicator needle stops and turns the other way, this is the maximum cam lobe lift. Note this down and set the piston back at TDC and do the same check to the other valves but should make sure that each piston should be at TDC on the side of the cylinder that you are about to check. This calls for inspection of lobes whereby their lift is checked against the camshaft specifications; if the lobe lift is below this value then the camshaft has worn and thus requires replacement. For removal - destroy the intake manifold with rocker arms with push rods and timing chain as well as the sprocket of the camshaft together with the crudities like the fan shrouds, water pump, radiator, and A/C condenser. They can be removed by use of a tool or a magnet if small; do not use pliers except when replacing the Lash Adjusters. Some of the roller Lash Adjusters require removal of the retainer and restrictors before withdrawal can be made. Provide a small box where you will store all your Lash Adjusters to ensure that they retain their positions for reuse. If the engine has a balancer shaft the drive gear is removed from the camshaft. Again observe the direction of the camshaft retainer before you unscrew it and, using bolts which are fitted into the camshaft sprocket bolt holes, pull out the camshaft from the block carefully without damaging the bearings. Generally, different camshaft bearing demand unique sort of tools in their replacement and it is highly advisable to undertake this process at the automotive machine shop. For installation, it is required that before installing the camshaft, the camshaft bearing journals and lobes must be lubricated, to later slide the camshaft into the engine, it has to be rotated until the dowel pin is at the 3 o'clock position while being supported. Place back the camshaft retainer in place and tighten the bolts that are holding it, then put in the balancer shaft drive gear such that the marks touch perfectly. If the timing chain has been replaced, or if any of the sprockets have been removed, put the new or cleaned and refurbished timing chains and sprockets in the engine compartment. If the Lash Adjusters have been removed for cleaning, lubricate them with fresh engine oil and put them back in their original positions if possible. As with any other assembly work, complete the remaining steps in the reverse order, and prior to starting the engine turn it over by hand to prepare for the installing a new oil and new oil filter.

Before removing the camshaft, test the lobe lift to verify how much wear has occurred on the cam lobes. First, set number one piston at TDC on compression stroke. Then loosen rocker arm nuts and pivot the arms sideways. Thereafter fit a dial indicator over the engine, and set its stem touching top of first pushrod. Zero 0 Dial Indicator as well as slowly rotate crankshaft in normal direction until needle of indicator stops and begins to move in opposite way. Record this reading then replicate for every other valve. Where the maximum value of cam lobe lift is below that specified, install a new camshaft. Take off the intake manifold, rocker arms, push rods, timing chain and cam sprocket from the head prior to removing it from cylinder block; unfasten balancer shaft drive and driven gears if any; draw out camshaft very cautiously holding it at near block area; after removal look up bearing journals if they were worn out or damaged; inspect with micrometer bearing surfaces for increased clearances or ovality conditions; also review cams for discoloration as well as scoring marks being present; wash out lash adjusters and verify them under light projections or even examining several pittings or variable wear patterns; take off old gear roller followers too when replacing lobes including wipers along with it only; check rollers on roller type Lash Adjusters for wear/scoring/any damage that might be noticed therefrom/moly based grease/lube oil between lobes besides journals/insert nozzle into a hole (where not abraded), which must be careful at all costs not to scrape groove bearings. Next Lubricate all journals both lateral zones plus lopes with molly base greases or assembly compounds intended strictly for engines respectively: insert executive's element without scratching related beds but before enjoying harmonic aspect together by looking whether matching bones actually are still available plus need refitting them again: finally, oil changes should chiefly concern replacement of filters too then engine run on.

After removing the camshaft from the engine, clean it with solvent and dry it, then inspect the bearing journals for uneven wear, pitting, and evidence of seizure; if damaged, both the camshaft and bearings will need replacement. Measure the inside diameter of each camshaft bearing, taking two measurements at each bearing, and subtract the bearing journal diameters from the corresponding bearing inside diameter measurement to obtain the oil clearance; excessive clearance necessitates new bearings. Camshaft bearing replacement requires special tools and expertise, so it is advisable to take the block to an automotive machine shop. Check the camshaft lobes for heat discoloration, score marks, chipped areas, pitting, and uneven wear; if the lobes are in good condition and the lobe lift measurements are as specified, the camshaft can be reused. Good used roller lifters can be reinstalled with a new camshaft, and while the original camshaft can be used if new lifters are installed, it is recommended to replace both together, especially for high-mileage engines. For V6 engines, if the balance shaft is to be removed, the balance shaft gear bolt should be removed before the timing chain to hold the shaft while loosening the bolt. Remove the two bolts and the balance shaft retainer at the front of the block, then use a slide-hammer threaded into the front of the balance shaft to knock it out. Inspect the balance shaft and measure the bearing journal diameters; if measurements exceed specifications, replace the balance shaft, bearing, and bushing as a set. The rear bushing, similar to a camshaft bearing, must be installed by a machine shop with the proper tools and alignment. Inspect the balance shaft drive gear and the balance shaft driven gear for signs of wear, pitting, broken teeth, or rough operation, as both gears are serviced only as a set.

After removing the camshaft from the engine, clean it with solvent and dry it, then inspect the bearing journals for uneven wear, pitting, and evidence of seizure; if damaged, both the camshaft and bearings will need replacement. Measure the inside diameter of each camshaft bearing, taking two measurements at each bearing, and subtract the bearing journal diameters from the corresponding bearing inside diameter measurement to obtain the oil clearance; excessive clearance necessitates new bearings. Camshaft bearing replacement requires special tools and expertise, so it is advisable to take the block to an automotive machine shop. Check the camshaft lobes for heat discoloration, score marks, chipped areas, pitting, and uneven wear; if the lobes are in good condition and the lobe lift measurements are as specified, the camshaft can be reused. Good used roller lifters can be reinstalled with a new camshaft, and while the original camshaft can be used if new lifters are installed, it is recommended to replace both together, especially for high-mileage engines. For V6 engines, if the balance shaft is to be removed, the balance shaft gear bolt should be removed before the timing chain to hold the shaft while loosening the bolt. Remove the two bolts and the balance shaft retainer at the front of the block, then use a slide-hammer threaded into the front of the balance shaft to knock it out. Inspect the balance shaft and measure the bearing journal diameters; if measurements exceed specifications, replace the balance shaft, bearing, and bushing as a set. The rear bushing, similar to a camshaft bearing, must be installed by a machine shop with the proper tools and alignment. Inspect the balance shaft drive gear and the balance shaft driven gear for signs of wear, pitting, broken teeth, or rough operation, as both gears are serviced only as a set.

It is important to keep the valve lifters and pushrods in order during the removal and installation of the 4.5L and 4.9L engines.

Compare the results to the specifications; if the lobe lift is below the specified value, a new camshaft is necessary.

When installing, lubricate the camshaft journals and lobes, slide the camshaft into the engine, and turn it until the dowel pin is in the correct position.

To remove the camshaft, you should first remove the intake manifold, rocker arms, pushrods, timing chain, and camshaft sprocket. If applicable, also remove the balancer shaft drive and driven gears. Carefully pull the camshaft out, supporting it near the engine block.

Remove the balance shaft gear bolt before the timing chain to hold the shaft while loosening the bolt.

It is recommended to replace both the camshaft and lifters together, especially for high-mileage engines.

Mount a dial indicator with the stem resting on the end of the exhaust valve pushrod, ensuring the plunger is in line with the pushrod.