Ensure the engine block and crankshaft have been completely cleaned, inspected and repaired or reconditioned before starting to reassemble the engine. Put the engine bottom up and remove the main bearing cap bolts, placing them in an orderly manner for proper installation. If there are still old bearing inserts at their places, remove them from both the block and main bearing caps. Clean the main bearing surfaces of the block and caps cautiously; keep them free from any debris. After that, clean the back sides of new main bearing inserts. Place one bearing half in each block's main bearing saddle first ensuring that tab on insert aligns with recess and oil hole in block matches insert. Do not hammer or damage faces of bearings during this process neither use any lubricant. The flanged thrust bearing must be installed in the rear cap and saddle. Clean when you are done with cleaning all bearing faces and crankshaft main bearing journals making sure to check and clean oil holes of crankshaft as well.Carefully position it in place within mains with assistance from someone else if required.Before installing crankshaft permanently, it is important to check main bearing oil clearance.Cut several small pieces of Plastigage into appropriate lengths; place these across each crankshaft's main journal.Put down all main cap bolts so that they face forwards towards front of engine.Tighten the caps' bolts following a careful sequence without rotating shaft.Remove bolts then caps making sure that Plastigage has not been disturbed.Compare widths of squashed Plastigage on each journal against scale on Plastigage envelope to find out what is your oil clearance.Correct any variations as needed afterwards scrape off all paper materials from major journal surfaces and faces without causing any other harm.The last step in putting crankshaft in place is applying thin even layer of clean moly-base grease or engine assembly lube onto surfaces below the bearings within block taking care to coat thrust faces properly.Put back the crankshaft into place in block again clean the surfaces of caps' bearings, apply lubrication and put on caps having arrows facing forward.Slightly tighten cap bolts in a specific sequence with reference to specified torque levels.Move handle to check if it is binding and inspect end play using feeler gauge or dial indicator for any runout.Finally, depending on engine type and model year, install such components as pilot bearing or crankshaft rear oil seal and housing.