[Mike Taylor 3601]

melling M-55A is heavier casting, m55 and m55hv have lighter castings,some things that will break pump are cavitation most of time pickup too close or far away from pan,or oil getting away from pickup or lack of oil, out of balance or vibration from driveline, oil pump shaft rubbing block some blocks need hole opened up or shaft that is undercut, some dart blocks need drilling for clearance around oil pump shaft.
Mike Taylor 3601