Main bearings for the engines are available in standard sizes and a range of undersizes to suit reground crankshafts. Clean the backs of the bearing shells and the bearing locations in both the cylinder block and the main bearing caps. Press the bearing shells into their locations, visually centralising each shell without touching the bearing surface with fingers. Note that all upper bearing shells have oil holes and are sometimes grooved, while the lower shells are plain. Wipe the shells dry with a lint-free cloth and lubricate each bearing shell in the cylinder block/crankcase with clean engine oil. Use a little grease to stick the upper thrustwashers to each side of the No 3 main bearing upper location, ensuring that the oilway grooves face outwards. Lower the crankshaft into position and check the crankshaft endfloat. Thoroughly degrease the mating surfaces of the cylinder block and the main bearing caps, then lubricate the lower bearing shells in the main bearing caps with clean engine oil, ensuring centralisation. Fit the main bearing caps using the identification marks for correct installation and insert the retaining bolts, tightening them by hand only. Working in sequence from the centre outwards, tighten the bearing cap retaining bolts to the specified Stage 1 torque setting, then tighten through the specified Stage 2 angle, checking that the crankshaft rotates freely before proceeding. Finally, fit the piston/connecting rod assemblies and, for diesel engines, install a new crankshaft left-hand oil seal.