I also checked for complaints about MELLINGS OIL PUMPS and they have alot of complaints.. I must have gotten 2 bad pumps.
Not necessarily the pump.
(You didn't indicate what was wrong about them.)
A few things to consider.
2 brand new Melling pumps
in a row being bad would be highly suspect-in my experience. But being given the wrong pump for your APPLICATION is quite possible.
You did try priming the pumps by hand before installing-to see if they worked then, right? And also checked the SIZE of the hex recess in each pump, against the
OLD rod size, right?
Ford used 2 drive rod diameters in the older cars, 1/4" and 5/16".
The 1/4" rod is used
mostly on the 302 and smaller engines, while the 5/16" is mostly used on 351's and and above.
Its not unheard of for a "substitute" pump to be in a
factory engine when parts shortages are going on. If, FOR EXAMPLE you were sent a 5/16" drive pump
but your particular engine uses a 1/4" drive rod, that would be the simplest explanation. Whether it came that way from the factory or someone put the wrong pump in for the application, or someone swapped DISTRIBUTORS at some point.
(And sometimes aftermarket suppliers will not stock pumps for
every year/engine application or show a pump mating with parts where it shouldn't, or have a typo creep in for the pump number.)
Barring that.
Mehanical rotor oil pumps are very simple, they either work or they don't-but the reasons for one no longer working can be one of several.
RARELY, the hex drive
ROD right at the pump or distributor end will get rounded off enough to not drive the pump, but if lubrication at
both ends of the drive rod is good, if the pump jams, usually the drive rod will snap before then.
MANY PEOPLE NEVER LOOK CLOSELY AT OR **** THE TOP END OF THE DRIVE ROD because if the original thin push nut/clinching washer is still there, it stays up in the engine.
The problems with the drive rod usually stem from hard crud or gasket material making it through the screen, which then puts a LOT OF BACK PRESSURE on the pump and eventually jams the pump rotor. Its also possible from a large accumulation of varnish or metal shavings to do the same thing.
Its not unknown for the hex recess in the distributor or that end of teh rod to wear
just enough for the rod to not be turning when the distributor is. Or for the roll pin that holds the distributor DRIVE GEAR onto the distributor shaft to shear. If
THAT happens the gear is no longer locked onto the shaft and the drive rod won't be turning.
And then there's the bugaboo of a stuck OPEN
oil pressure relief valve not allowing oil pressure to build sufficiently.....
If you have one of those, and it went on for some time with the engine running, there may have been be a lot of engine damage happening to bearings.