Quote:
Originally Posted by jeepguy1948
So, I just bought a freshly rebuilt “B” motor (with weighted crank). I was told that it had a “drilled crank” I ham some idea what that means but I know that I could learn more here. In addition, I’m wondering if it would still be a good idea to oil that center main direct or if that is taken care of by the drilled crank. BTW it is using Babbitt (which sort of disappoints me because I can’t replace the bearings myself but I doubt that they will need replaced in my lifetime LoL)
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This is something that is often misunderstood about bearing conversions. From my experiences, probably 90+% of the time when insert shell bearing wear the alloy off of the shell, the metal bearing shell starts wearing against the crankshaft's journal pin. When this happens, at some point it generally rolls the bearing inside of the journal and cap. Unlike a cast bearing where you hear excessive clearances, most everyone says it just suddenly started rattling and then started seizing up.
Every block that has come thru here that has spun an insert bearing, it generally distorts the main cap or kills the rod. The thickness of that insert shell must go somewhere, and something has got to give!! While there are some guys that will 'butcher' it back together by polishing the journal pin and slapping a new pair of inserts in it, the proper way is to either replace the damaged main cap or re-size the existing cap. Either way, it generally takes line boring again or at least line honing again to get all mains the proper size to crush the bearings, -AND coplanar again. Most hobbyists do not have that capability, so they cannot replace the bearings themself anyway.
