GM 14002534 BEARING

Check the bearing surfaces and the surface of the cam lobes; light pitting or scratching may be smoothed with fine emery cloth or an oil stone, but if the camshaft is deeply scored a new one will be necessary. Camshafts should be mounted on V-blocks and employed with a dial gauge to measure camshaft lobes lift and run-out and exclude camshafts that do not meet the stipulated camshaft lobe lift and run-out. Use a micrometer to measure the journal diameters; it is mandatory to scrap any camshaft which does not conform to the above limits. In the case where either camshaft bearings are worn out or in some conditions damaged, then they have to be replaced; it can be done by having to detach the crankshaft but maintaining cylinder heads and pistons. To avoid getting damaged, the connecting rod bolts should be taped before the removal of the crankshaft and the connecting rods should also be taped to the side of the engine to minimize on interference when removing the bearings. Take out the camshaft rear cover from the top of the cylinder block. Bearing can be removed using GM tool part number J-6098 or a like bearing remover / installer tool according to the instructions. The same set of tools is used to set the camshaft bearings where, for instance, the front and the rear bearings help in centering the remainder of the bearings so that the oil hole in the bearings will match the oil hole in the block. Remove any debris, oil or old gasket material from the camshaft rear cover, then give the cover a layer of RTV or any other equivalent sealant with 1/8 in x 3mm diameter around the sealing surface before fixing the cover on the engine block. Finally, reinstall the crankshaft.

Remove the engine and install it on a suitable stand, then take off the rocker arm cover. Loosen the rocker arm nuts and pivot the rocker arms clear of the pushrods, or remove the bolts and lift the rocker arms off in later models. Next, remove the pushrods, pushrod cover, valve lifters, distributor, fuel pump, oil pump drive shaft and gear assembly, front pulley hub, and timing gear cover. Remove the two camshaft thrust plate screws by working through the holes in the camshaft gear, then support the camshaft with fingers inserted through the fuel pump hole to prevent damage while carefully pulling it straight out from the block. If the gear needs to be removed from the camshaft, it must be pressed out; if a press is unavailable, consult a dealer or automotive machine shop, ensuring the thrust plate is positioned correctly to avoid damage during this process. Examine the bearing surfaces and cam lobes, removing the oil pan if necessary for thorough inspection. Shallow surface scratches can be smoothed with fine emery cloth or oilstone, but deep scoring requires a new camshaft. Mount the camshaft on V-blocks and use a dial gauge to measure lobe lift and run-out, rejecting any that do not meet specified limits. Measure the journal diameter with a micrometer, rejecting any camshaft that fails to meet the limits. If the camshaft bearings are worn, remove the oil pan and flywheel, then drive out the expansion plug from the rear cam bearing, followed by the front bearing toward the rear and the rear bearing toward the front using a camshaft bearing remover set. Drive out the center bearing toward the rear, then install new bearings by reversing the removal procedure, ensuring all oil holes are aligned, and drive the front bearing approximately 1/8 inch from the front of the cylinder block to uncover the oil hole for the timing gear oil nozzle. After installing the new bearings, install a new camshaft rear expansion plug flush with the rear surface of the block, then reinstall the flywheel and oil pan. If the camshaft gear has been removed, it must be pressed on before installation by supporting the camshaft in an arbor press, placing the gear spacer ring and thrust plate over the end of the shaft, installing the woodruff key, and pressing the camshaft gear onto the shaft until it bottoms against the gear spacer ring. Check the end clearance of the thrust plate with a feeler gauge, replacing the spacer ring if clearance is less than .0015 inches or the thrust plate if more than .0050 inches. Before installing the camshaft, ensure that number 1 cylinder is at TDC and coat each of the lobes and journals with lithium-based grease. Slide the camshaft into the engine block, taking care not to damage the bearings, and position the camshaft and crankshaft gears so that the valve timing marks align, indicating the engine is in the number 4 cylinder firing position. Install the camshaft thrust plate mounting screws and torque to specifications, then complete the installation by reversing the removal procedure, ensuring to rotate the engine 360° to the number 1 cylinder firing position when installing the distributor.

A dial gauge is used to measure lobe lift and run-out.