CHECKING BEARING CLEARANCE
- Remove bearing cap and wipe oil from crankshaft journal and outer and inner surfaces of bearing shell.
- Place a piece of plastic gauging material in the center of bearing.
- Use a floor jack or other means to hold crankshaft against upper bearing shell. This is necessary to obtain accurate clearance readings when using plastic gauging material.
- Reinstall bearing cap and bearing. Place engine oil on cap bolts and install. Tighten the bolts to specification.
- Remove bearing cap and determine bearing clearance by comparing the width of the flattened plastic gauging material at its widest point with graduations on the gauging material container. The number within the graduation on the envelope indicates the clearance in millimeters or thousandths of an inch. If the clearance is greater than allowed, REPLACE BOTH BEARING SHELLS AS A SET. Recheck clearance after replacing shells. (Refer to Main Bearing Replacement.
Main bearing clearances must be corrected by the use of selective upper and lower shells. UNDER NO CIRCUMSTANCES should the use of shims behind the shells to compensate for wear be attempted. To install main bearing shells, proceed as follows:
- Remove the oil pan as outlined elsewhere in this section on some models, the oil pump may also have to be removed.
- Loosen all main bearing caps.
- Remove bearing cap and remove lower shell.
- Insert a flattened cotter pin or roll out pin in the oil passage hole in the crankshaft, then rotate the crankshaft in the direction opposite to cranking rotation. The pin will contact the upper shell and roll it out.
- The main bearing journals should be checked for roughness and wear. Slight roughness may be removed with a fine grit polishing cloth saturated with engine oil. Burrs may be removed with a fine oil stone. If the journals are scored or ridged, the crankshaft must be replaced. The journals can be measured for out-of-round with the crankshaft installed by using a crankshaft caliper and inside micrometer or a main bearing micrometer. The upper bearing shell must be removed when measuring the crankshaft journals. Maximum out-of-round of the crankshaft journals must not exceed .037 mm (.0015 in.).
- Clean crankshaft journals and bearing caps thoroughly before installing new main bearings.
- Apply special lubricant, No. 1050169 or equivalent, to the thrust flanges of bearing shells.
- Place new upper shell on crankshaft journal with locating tang in correct position and rotate shaft to turn it into place using cotter pin or roll out pin as during removal.
- Place new bearing shell in bearing cap.
- Install a new oil seal in the rear main bearing cap and block.
- Lubricate the removed or replaced main bearings with engine oil. Lubricate the thrust surface with lubricant 1050169 or equivalent.
- Lubricate the main bearing cap bolts with engine oil.
In order to prevent the possibility of cylinder block and/or main bearing cap damage, the main bearing caps are to be tapped into their cylinder block cavity using a brass or leather mallet before attaching bolts are installed. Do not use attaching bolts to pull main bearing caps into their seats. Failure to observe this information may damage the cylinder block or a bearing cap.
- Torque the main bearing cap bolts to 145 N·m (107 ft. lbs.).