GM 91177626 Engine Crankshaft

Remove all burrs from the crankshaft oil holes with a stone, file or scraper, ensuring the oil holes are chamfered to prevent damage to new bearings. Check the main and connecting rod bearing journals for uneven wear, scoring, pits and cracks. Rub a penny across each journal several times to reveal its condition-if copper rubs off and is embedded in the crankshaft, the journals should be reground. Clean the crankshaft with solvent and dry it with compressed air, using a stiff brush to clean the oil holes and flush them with solvent. Check the rest of the crankshaft for cracks and other damage, which should be revealed by mag-nafluxing. Measure the diameter of the main and connecting rod journals with a micrometer and compare the results to the Specifications. If the crankshaft journals are damaged, tapered, out of round or worn beyond the limits given in the Specifications, have the crankshaft reground by an automotive machine shop and use the correct size bearing inserts if the crankshaft is reconditioned. Check the oil seal journals at each end of the crankshaft for wear and damage. If the seal has worn a groove in the journal, or if it's nicked or scratched, the new seal may leak when the engine is reassembled. In some cases, an automotive machine shop may be able to repair the journal by pressing on a thin sleeve. If repair isn't feasible, a new or different crankshaft should be installed. Examine the main and rod bearing inserts.

In DOHC engines, the crankshaft is secured to the block using a "lower crankcase" instead of traditional main bearing caps.

New main bearing inserts should be placed in each main bearing saddle within the block without using lubrication, ensuring proper alignment and fit.