I've acquired another with a standard piston style bypass. It was listed as a Melling HV HP oil pump. It didn't come in any box but it looks brand new.
The tag has HM42 and 91282. The bottom plate looks cast with HP cast into it. The main casting itself has 542 on one side and on another side, 5201 with a larger 2 to the right, with a diamond shaped logo which looks like it has the letters BCI in it. I like the shape of the cover. It provides a way to tell how to orient the cover. On the stock ones, it's not so obvious. Minor detail but nice if you take it apart. The rotors are the same depth as stock so it's not a HV (High volume) pump. None of the cover plate bolt holes are counterbored in this unit. Come to think of it, that counter bored hole in the other may be for easier orientation of the cover to that unit.
The pump housing is most similar to an original ECG pump. The cover plate end is clocked differently on a C1AE pump.
ECG left, Iron right.
The most apparent difference that may have any effect on performance (HP?) is the size and shape of the cavities in the housing, the passage to the engine is more open and about .050" larger in diameter and the bypass passage into the rotor cavity is larger. That bypass passage looks to be as cast in the iron unit and drilled in the originals.
I don't know if my other is similar in these areas. I don't have pictures with the rotors removed and it is at Ted's at the moment. That one wasn't advertised as anything special so I didn't think to take a closer look.
Iron:
C1AE:
ECG:
The bypass piston is different from the stock gerotor pumps I've taken apart but looks to be the same as at least one piston I have removed from a spur gear pump.
Center and left, original gerotor. Right Iron:
Differences on the block side.
C1AE left, Iron Right:
ECG left, Iron right:
Lawrenceville, GA