On engines with flanged thrust bearings, it's important to "set" the thrust bearing during assembly. This ensures that the thrust bearing is firmly shouldered against the main-cap and block in the forward direction of thrust. To "set" the bearing, slack the main fasteners at the thrust bearing position, and then run them in until they are seated. Using a heavy soft-face mallet, smack the nose of the crank rearward. Next, use the same arrangement at the rear rank flange to smack the crank forward. Now torque the main cap as normal.