New babbitt compresses and glazes over, and this will increase oil clearance. Usually though, if you can't hear it then you're o.k.. BUT, if you hear the slightest hint of a knock then tighten the bearings RIGHT NOW. Don't continue to run the engine.
I have always advised people, who are installing a Brumfield Head on an older engine, to check all the bearings before installing the head whether they can hear anything or not. Even though no noise is heard, the clearances might be excessive enough that they're not far from it. Adding on a head like a Brumfield at this point, which produces considerable torque, may pound the bearing a little on a hard run.
Larry B.