TM 10-3930-660-34 3-9.  CRANKSHAFT MAIN BEARINGS - REPLACE (Cont’d) NOTE Install  bearing  halves  dry  for   the   following clearance checks. c. Install a dry upper bearing half (3) over the crankshaft journal for main bearing number 1  such  that  the  bearing  tab  will  fit  into  the notch    in    cylinder    block.        If    used    main bearing    is    being    installed,    install    main bearing   half   in   the   same   position   it   was removed from. CAUTION Be very careful not to scratch the crankshaft or the bearing bore during the installation of the  upper  bearing  halves.    A  scratched  or damaged crankshaft, or bearing bore, could result in premature engine failure. d. Simultaneously    push    the    upper    bearing half, with a  flat  blade  screwdriver,  and  turn the  crankshaft  until  bearing  tab  is  in  notch in cylinder block. e. Install  a  dry  lower  main  bearing  half  (4)  in number  1  main  bearing  cap  (2).    Tab  on bearing   must   be   in   the   notch   in   bearing cap.        If    used    main    bearing    is    being installed, install bearing in the same bearing cap it was removed from. f. Place   plastigage   on   the   surface   of   lower main bearing half (4). 3-77