Chevrolet 12686787 Valve Lifter

This operation is a somewhat complicated one, and it employs instruments that are specific to it, so make sure you read through all the directions and make sure you have all the tools you will need ready before beginning the operation. On the first step, you must unplug the cable from the negative terminal on the battery, and on the second step, take off the valve cover. Place the engine at TDC of cylinder number one and rotate the crankshaft in anti-clockwise direction to position the crankshaft at 60 degrees before TDC, while positioning the diameter shaped hole at twelve o clock position on intake camshaft. Secondly, take off the upper timing chain guide and place a particular tool that will immobilise the camshaft sprockets. Remove the bolts on the camshaft sprocket and put the sprockets aside, in addition, loosen the wing nuts that lock the sprockets in place. Another feature is that each camshaft cap features a number, which shows the position of the camshaft; each bearing cap bolt should be loosened gradually but firmly enough to lift the camshaft from the cylinder head. Take out the rocker arms while in so doing retain them and the hydraulic lash adjusters so that they can be refitted. Remove the exhaust bearing caps followed by the rocker arms and the lash adjusters in like manner. Each hydraulic lash adjuster needs to be checked for wear and each of them needs to have its diameters measured; if the lash adjusters are out of round, they will have to be exchanged. Inspect the rocker arms for any signs of wear or damage, the camshaft lobes also for wear, the thickness of the lobe and if there is a massive variation replace the camshaft. Check the camshaft bearing journals for wear and measure the diameter of each; replace any that do not conform to minimum size. To check the bearing journal oil clearance, all the bearing surfaces must be cleaned, followed by installing the camshafts together with the bearing caps with Plastigage across the journal, and as the bolts are tightened, the width of the flattened Plastigage is then to be measured. If any oil clearance is over the service limit, then the camshaft, or the cylinder head should be replaced. On camshaft end play, the bearing surfaces must be cleaned and the camshafts and bearing caps put in place before using a dial indicator to check on the end play. If the endplay is at any time beyond the service limit, it is advisable to replace either the camshaft thrust cap or the camshaft. For assembly, apply oil to the rocker arms and the lash adjusters and then position them as earlier used. Oil the camshafts and then place it properly and follow through the camshaft bearing s which have to be tighten in sequence. Move the camshaft sprockets and the timing chain right to the camshafts, so that the slots get into the corresponding projections on the sprockets and screw new bolts. Take out the camshaft locking tool, screw and tighten the front and rear camshaft cap to the recommended torque. The upper timing chain guide must be fitted, and the engine has to be rotated by hand in order to feel the level of the resistance. Finally, reconnect the battery.