TM 9-2815-237-34 2-41.  ENGINE  ASSEMBLY  FROM  SUBASSEMBLIES  (Cont’d) NOTE l During assembly operations, it is important to closely inspect each unit to make sure nothing has been overlooked during inspection and repair. Plugs  should  be  checked  for  tightness,  parts  kept  clean,  openings covered, and machined surfaces protected. Application of lubricant should  be  performed  from  covered  containers. l Work area should be clean, well-ventilated, and free of blowing dirt and  dust. l In some cases, flanged head fasteners may be present instead of standard fasteners and washers. In all cases, washers should be used when replacing a flanged head fastener with a standard fastener. l For general assembly instructions, refer to para. 2-12. l Assembly procedures for pre-1990, 1990 and above 6.2L and 6.5L engines  are  basically  the  same.  Any  differences  in  procedures  are  noted. Some  replacement  parts  are  different.  Refer  to  para.  1-10  to  determine engine  model  before  ordering  replacement  parts. a. Crankshaft and Main Bearings NOTE l Measure outside diameter of crankshaft main bearing journals to determine  what  thickness  main  bearings  to  install. l Main bearings are of the precision insert type and do not utilize shims for adjustment. If clearances are found to be excessive, a new bearing, both upper and lower halves, will be required. Service bearings are available in standard  size  and  undersize. l Selective fitting of both rod and main bearing inserts is necessary in production in order to obtain close tolerances. For this reason you may find one-half of a standard insert with one half of a 0.001 in. (0.025 mm) undersize insert, which will decrease the clearance 0.0005 in. (0.013 mm) from using a full standard bearing. 1. Remove all capscrews (1) and (2) and bearing caps (3) and install upper halves of main bearings (7) in  cylinder  block  (6). 2. Install lower halves of main bearings (4) in bearing caps (3). Crankshaft must be supported during removal and installation. Failure to support  crankshaft  may  cause  injury  to  personnel  or  damage  to  equipment. 3.  Install  crankshaft  (8)  in  cylinder  block  (6). NOTE The gaging plastic shall be positioned the full width of the bearing and centered on the bearing journal when the bearing cap is installed. 4. Position gauging plastic on bearing journal (5) the full width of the bearing (4) and parallel to the center  line  of  the  crankshaft  (8). 2-154