TM 10-3930-659-34 5-4. ENGINE MAIN BEARINGS, THRUST BEARING, AND CRANKSHAFT REPLACEMENT (Con’t). CAUTION Upper  main  bearings  and  main  bearing  caps  must  be  installed  on  engine  block  as  noted  during removal. Failure to do so may damage parts. NOTE Measurement of inside diameter of one main bearing is described in steps 10 through 18. 10. Position   upper   main   bearing   (13)   on   engine block    (5).    Ensure    that    tang    on    upper    main bearing fits in locking groove on engine block. 5-39