Complex sentence: They did not have conventional rod bearings-they had rods made from babbitt and there were thin copper shimms, between bottom of rod cap and the actual connecting rod, as the rod wore out shims had to be removed.
Split into simpler sentences: They did not have conventional rod bearings-they had rods made from babbitt with thin copper shims between the bottom of rod cap and the actual connecting rod. As the rod wore out shims had to be removed.