GM 91177510 Engine Crankshaft (On Esn)

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The crankshaft can be removed only after the engine has been removed from the vehicle. Before removing the crankshaft, it is important to check the end play. This can be done by mounting a dial indicator with the stem in line with the crankshaft and just touching one of the crank throws. Push the crankshaft all the way to the rear and zero the dial indicator, then pry the crankshaft to the front as far as possible and check the reading on the dial indicator to determine the end play. If the end play is greater than specified, the crankshaft thrust surfaces should be checked for wear. If no wear is evident, new thrust bearings should correct the end play. If a dial indicator is not available, feeler gauges can be used to determine the clearance. Gently pry or push the crankshaft all the way to the front of the engine and slip feeler gauges between the crankshaft and the front face of the thrust bearing to determine the clearance. On SOHC engines, it is important to check the main bearing caps to see if they are marked to indicate their locations. They should be numbered consecutively from the front of the engine to the rear. If they are not marked, they should be marked with number stamping dies or a center punch. The main bearing caps should be loosened gradually and removed by hand, noting the location of any stud bolts. The caps can be tapped with a soft-face hammer to separate them from the engine block. On DOHC engines, there are no crankshaft main bearing caps. Instead, a "lower crankcase" is used to secure the crankshaft to the block. To remove the lower crankcase, the bolts should be removed in the indicated sequence. Carefully lift the crankshaft out of the engine, taking care due to its weight. With the bearing inserts in place in the engine block and main bearing caps, the caps should be returned to their respective locations on the engine block and the bolts tightened finger tight.

Removing burrs from the crankshaft oil holes is essential to ensure proper oil flow to the engine components and prevent damage to new bearings.

After positioning the engine bottom up, the next step is to remove the main bearing cap bolts and gently lift out the caps, arranging them in the correct order for accurate reinstallation.