Insert bearings

[Synchro909]

Originally Posted by Jack Shaft

Spiral grooving and increasing clearance can have a negative effect on the oils ability to support the crankshaft.Modern oils have better load carrying properties,so opening the clearance to .002 works but resist the desire to do more.Any grooving on the bottom of the bearing (center of the cap) reduces the cushion effect in the area of the groove.Given what your experiencing Id say is a failure of the babbit adhering to the copper of the insert,not a lubrication issue.

There is no copper evident in the insert. What you say about a groove in the bottom compromising lubrication, I suspected. That is why I asked.