I was starting to look at my main bearing inserts and noticed they have notches near the edge of the parting line. They look like the notches that modern caps have to retain the insert.
Narrow caps only have one and the larger #1 with the thrust surfaces has 5. Are these for oil retention, alignment or ??? Inquiring minds want to know.
They are for collecting dirt/contaminants and keeping them from grinding the journal as much. The greatest pressure is on the bearing on the top and bottom shell, right in the center, pure up and down forces.
there is very little dis force on the crankshaft.