Crankshaft installation is the first task in reassembly of the engine and this is on condition that both the engine block and crankshaft have been washed, checked and mended as may be necessary. Sitting the engine on its bottom, unscrew the main bearing cap bolts and take off the caps, put them somewhere to fit them back again in the same formation. If present, the original bearing inserts have to be detached from the block and caps and the bearing surfaces dealt to be free from contaminants. Degrease the back sides of the new main bearing inserts and then fit one in each main bearing saddle in the block; make sure that the grooved insert is in the right place and the oil holes match up. Thrust bearing inserts: For specific engine types, make the following installations: Scrape the bearing faces and crankshaft main bearing journals and place the crankshaft in position having the connecting rods oriented upwards. The main bearing oil clearance should be checked using Plastigage and placed correctly on the journals before the associated caps are replaced. To adjust the main bearing cap bolts, tighten them by three quarters of a turn in one operation without spinning the crankshaft; thereafter, unscrew the caps in order to check the Plastigage width for the purpose of determining the clearance. If the clearance is incorrect, don't look immediately at different bearing inserts, but examine for dirt or oil interference. Having cleared the Plastigage off, withdraw the crankshaft and make sure the bearing surfaces in the block are clean; some sealer, greasier or assembly lube is to be applied. Place the crankshaft back into the same position, apply lubricant on the bearing surfaces of the caps and reposition them in their rightful positions the arrow part facing forward. Loosening of bolts should be done from the outer periphery of the engine and move inwards and then tighten the thrust bearing cap bolts. Using a soft hammer strike the ends of the crankshaft thrust surfaces to bring the surfaces opposite each other into alignment, then re-torque all main bearing cap bolts, and rotate the crankshaft, checking for binding. Lastly, examine the crankshaft endplay by inserting a feeler gauge or dial indicator; the faces ought not to be worn and the new bearings should be fitted; fit a new rear main oil seal.