46 4 DLT ENGINE Measure pre tension of main bearing shell with a feeler gauge after loosening main bearing cap mounting bolt on opposite side of bearing shell lug. (This is to be done on a flat surface plate as it cannot be measured on engine cylinder block because the main bearing caps are guided) MAIN BEARING SHELLS ARE PRECISION FINISHED AND SHOULD NOT BE BORED OR SCRAPED. Select new pair of thrust washer according to crank shaft 4th main journal width. CYLINDER BORES Clean cylinder bores thoroughly. Check cylinder bore dimension, taper and ovality. Refer Figures. 74 & 75 If taper and ovality is found to exceed specified limit or bore is excessively worn out machine cylinder bore to next over size. Selection of size to which bore should be machined should be choosen as per following parameters : - Bore diameter of worn out cylinder bore - Size of next piston available - Recommended clearance between piston and bore - Required bore diameter Machine all bores leaving 0.050 to 0.070 mm stock for honing. IT IS VERY IMPORTANT THAT AXIS OF CYLINDER BORESAREPARALLELTOEACHOTHERANDARE AT RIGHT ANGLE TO AXIS OF CRANK SHAFT. Therefore we recommend use of pillar type boring and honing machines. Clean cylinder bores, bearing surface and oil passages in crank case thoroughly. Check water jackets and oil passages for leakages/ cracks at air pressure of 5 bar under water. Apply grease tomachined surfaces especially if engine assembly is not be taken up immediately. Fig. 74 Fig. 75
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