difference betwen old melling 72hv and new one.

Not so sure it has as much to do with flow per se, as it does with minimizing the pulses in output flow. There have been many articles written on the subject and no matter what the style of gerotor is used, the pumps output is never as smooth as a spur gear type pump. The gerotor pump also requires more pickup tube area for the same GPH output.

It's possible the updated version is looking to address one or both of these issues.


EDIT: Just one of many reasons why you don't oil a Chrysler like you do a chevy.