ACL's main bearings are made of a softer metal so that you don't wear out your crank or engine block. Additionally, a thin layer of oil lubricates the connection between the bearings and the crank allowing the crank to "float" and reduce wear. Proper support via main bearings is crucial to prevent oscillations and wear that can damage the crankshaft and other components as the motor moves further out of balance.
Bearings with extra oil clearance will absorb the stress of higher horsepower motors greater, but will see increased wear during start up. We recommend these be purchased by experienced professionals only.