Chevrolet 12604896 Camshaft Assembly, Exhaust

The camshaft bearing caps are numbered and lettered and are fitted with a raised arrow; the number refers to the bearing journal position from the front of the engine, the letter to the camshaft and the arrowhead is at the front. For this procedure, special timing chain holding tools EN 48383-2nd EN 48383-3rd are required; otherwise, the timing chain cover has to be detached in order to keep the chains connected to their lower sprockets. First of all, the negative battery cable should be disconnected, the valve cover(s) should be taken off, and depending on which camshafts are being removed the high-pressure fuel pump, for 3.0L, and the lower intake manifold, for 3.6L. Next to do, remove the Camshaft position sensors and the camshaft position actuator solenoid valves. Turn the engine over until the camshaft flats are parallel with the ground, measure the amount of In/Out and be very careful not to damage the camshaft. Lose the camshaft position actuator bolts, position the special tool to hold the timing chain and sprockets, then remove the actuator bolts. After the assembly place all the bearing caps in specifically marked box, unravel the camshaft bearing cap bolts in the reverse procedure that was used to tighten them, to do a check on the camshafts for wear or damages make use of the micrometer. Scrub the camshaft, check the bearing journals for any wear, measure the wear of the camshaft lobes and look for any signs of damage. Check the camshaft bearings and measure the bearing oil clearance; if clearance exceeds the standard it is usually advisable to replace the bearings and this is best done by a professional. For installation; before fitting the camshafts to the engine, the camshaft bearing journals and cam lobes needs to be lubricated, the correct position of the camshafts need to be ensured, the bearing caps need to be smeared with a layer of engine oil, and then the bearing caps have to be fitted to their correct position in the newly fitted camshafts. Loosen the bearing cap bolts and then assemble the cap back on the shaft and torque each of the bolt to required specifications. After ensuring the efficient working of the timing chain holding tool, start the engine and to finish the job reverse the whole process of removal. Before starting of the engine, it is required to replace the oil filter and to change the oil also.

It is always required to inspect the camshaft before assembling it, while end play must necessarily be measured before dismantling. The camshaft bearing caps have some numbers and letters on them; the number refers to the bearing journal of the camshaft, and the letter indicates whether it belongs to the intake or the exhaust side; the arrow also designates the front of the engine. For this, special timing chain holding tools EN 46108 or EN 48313 are required; if these are not available, the timing chain cover has to be taken off to guarantee correct connection of the chains to their lower sprockets. For the start of removal, the negative battery cable must be disconnected and also the valve cover(s) and the lower intake manifold and any other parts that may hinder the process. Next, take out the camshaft position sensors and at least one of camshaft actuator solenoid(s). Turn the engine so that the flats of the camshaft are on the top and dorsoventral to the surface of the cylinder head, then measure the camshaft end-float by pivoting a dial gauge. There may be a tendency to break the camshaft while turning the engine and therefore care should be taken to avoid this. Relax the camshaft sprocket bolts, put the timin g chain holding tools in place and mark the sprockets and the chain. Unbolt the camshaft sprocket and take off the sprockets, keep the bearing caps and store it in the box where you marked it. Bolts of camshaft bearing cap should be loosened a little at a time, in the reverse order of how they were tightened, and the camshafts must be checked for wear or damage. For installation, check if the sealing rings are properly in position and apply assembly lube on the bearing journals as well as on the cam lobes. Coat the bearing journals on the RH cylinder head and align the camshafts on it with the flat surfaces of the camshafts facing the surface of the valve cover gasket. Again put some engine oil on the bearing caps, screw the caps into the block as a sensible pattern and screw them by hand. Place his for head bolt and vice-vice using torque wrench tighten the bearing cap bolts in the order of M1 M2 M3 M4 M6 and re-check to ensure that the torque is adjusted. Do the same for the LH cylinder head camshafts as well as the number of turns of the crankshaft accessible from that area. Any doubts about the positioning of a timing chain holding tool should be resolved prior to engine ignition since chains and sprockets react to this step. The rest of the removal process is done in the reverse order and before engaging the engine, replace the oil and the oil filter.

To remove the engine, first to undo the bolt and clamp that is situated at the oil pump drive, then the oil pump drive should be pulled upwards and out of the block. Fourth, the timing chain, sprockets, as well as the valve lifters should be pulled out. Then remove the bolts with holding the camshaft thrust plate to the block surface and remove the thrust plate. Remove the camshaft by pushing it directly out of the engine using one long bolt as a lever and maintaining the support of the shaft at the block end with your hand; in this process try not to harm the bearings. If the camshaft has to come out, it is advisable to remove the bearings also, clean the camshaft with solvent, dry and inspect the bearing journals for signs of wear such as pitting or seizure etc, if they are damaged both the shaft and bearings will have to be replaced. This should be done using a micrometer on the bearing journals and on the camshaft lobes in order to check for conditions such as excessive wear or out of round and to measure the lobe lift by measuring at the largest and smallest points of the lobe. Check the camshaft lobes for any sign of dullness, scratching or wear, if the camshaft lobes are in good health and within legal size the camshaft can be regenerated. Gently rock the cam shaft to check the bearings in the block for deformation, galling or pits and the housing journals for any replacement. Measure the inside diameter of each bearing using an inside micrometers or a bore gauge; in calculating the bearing oil clearance subtract the camshaft bearing journal diameter from the inside diameter of each bearing; if clearance is in excess then new bearings will be required. Because camshaft bearing replacement undoubtedly means taking the block to an automotive machine shop, it would be better to do so. To install it, the camshaft bearing journals and the lobes must be lubricated with a special grease after which it should be slid into the engine using a bar and a long bolt, by holding it as close to the block as possible and also avoiding the bearing area. Lastly screw on the camshaft retainer plate and make sure that the camshaft sprocket bolts have been tightened to the recommended torque. For the oil pump drive, dip only the gear portion on fresh engine oil and screw it into the block so that it fits squarely against the mounting boss and then tightened by its retaining bolt. Also it is advisable to fit a new O-ring on the oil pump driveshaft before screwing onto the drive.

The removal of it turns out to be complicated and special tools are needed, new camshaft sprocket bolts, which you should probably buy every time. There are three special implements required to hold the timing chain relative to the cylinder head on the intake and the exhaust side. Then the pressure of the fuel system must be released and the negative terminal of the battery must be disconnected whereas the air filter housing, the ignition coils, the spark plugs, and the valve cover should be unbolted. The timing chain tensioner is then removed, the crankshaft is turned in order to place the special tool that will loosen the camshaft actuator bolts in place. All actuators are tagged for the re assembly and the upper chain guide is also taken off. Other tools are used to secure the timing chain before the removal of camshaft actuators and camshaft solenoids. Camshaft cap is identified by its location and orientation; the camshafts are lifted off the cylinder head but all the related accessories have to remain neat. The hydraulic lash adjusters are located on the heads or issuces of their respective rockers and properly storrage with the rockers. Lash adjusters, for example, are checked for wear or damage, and the measurements of the rocker arms as well as camshaft lobes are gone through to meet a specified gauge. Any elements, which are recognized as worn beyond their acceptable limit, have to be replaced. There is also the lubrication of the rocker arms and the lash adjusters, correct setting of the camshafts and the final tightening of the bearing caps as per a set sequence. Camshaft sprocket actuators and timing chain are put in position and screwed then timing chain tensioner is reprogrammed. Last of all, the upper timing chain guide is bolted and tightened and the battery connection is restored and the process is then done.

To remove the camshaft, first of all, unbend the terminal of the cable of the battery's negative pole. Third, it is pull the bolt and clamp which holds the oil pump drive and then pull out the oil pump drive upwards from the block. Then remove the timing chain, sprockets and valve lift as shown in the following image to you. Yank out the bolts that are holding the camshaft thrust plate to the block and then withdraw the thrust plate. Pull out the camshaft in a straight manner using a long bolt as a bar while resting your hand around it near the block, lest you damage the bearing. One removed, wash the camshaft in solvent, then dried, and checked for bearing journal for wear or damage, if any, then both camshaft and bearings will have to be replaced. The bearing journals and camshaft lobes must be checked with a micrometer to determining their wear or out of round conditions; the lobes must also be observed for discoloration or any signs of damage. The lobes are designed to exchange or throw oil and if the lobes are in good condition and measurements are within the specifications listed above then the camshaft can be reused. Camshaft bearings in the block should be checked for galling and discoloration as well as the housing journals. Measure the bearing's inside diameter of the bearing using the small hole gauge and the outside micrometer; to calculate the bearing oil clearance subtract the camshaft bearing journal diameter from the bearing inside diameter. Where the clearance has been allowed to be too high, new bearings or housings will be the requirement. Since the bearing in a camshaft is sensitive, replacement has to be done carefully; it is recommended for the block to be taken to an automotive machine shop. Before installing, coat the camshaft bearing journals and the cam lobes with special camshaft lube if available, after which the camshaft is slid into place on the engine with help of a long bolt that is passed through from the front of the block. Place the camshaft retainer plate as indicated above and fasten the bolts to the appropriate degree of turning out. Last but not the least the gear portion of the oil pump drive should be dipped in engine oil and fitted into the block in such a manner that it should be placed in contact with its mounting boss and the retaining bolt should be inserted next and with reference to the oil pump driveshaft a new O-ring to be fitted.

For these engines, remove the upper timing chain guide and use a special tool to secure the camshaft sprockets in place. Remove the camshaft sprocket bolts and slide the camshaft sprockets forward, securing them with wingnuts. If working on 2009 and later models, remove the camshaft position actuators; for 2008 and earlier models, remove the timing chain tensioner.

Before beginning, prepare the necessary special tools and acquire new camshaft sprocket bolts. Additionally, relieve the fuel system pressure on 2.0L supercharged models and disconnect the negative battery terminal.

Check each hydraulic lash adjuster for excessive wear, scoring, pitting, or an out-of-round condition.