Oil Pump Manufacturer?

Either should be good, but I would take Melling if the prices were close. Both brands used to be USA made, hopefully they both still are.
I still pick up ancient old-stock stuff that comes up on eBay.
-Donny

 

Just put Melling in my 304, was made in USA. Not an endorsement, I think theyre only vendor for AMC V8 oil pump gear sets.

 

compare if they are the same design gear vs starwheel thing.

 

What you described is called a Gerotor, these are superior in pumping quality but wouldn’t know if there was one made for engine design this old.

 

I remember someone did a full flow oil filter mod with one style or the other I thought it was a good idea. Filtering only the timing gear seems very... faithful.

 

Unless you find NOS, the only oil pumps out there are gear type - the "scroll and rotor" is not being made anymore. Truth be known, Melling makes all the "USA" oil pumps for themselves, Sealed Power , Elgin, etc - they "private label" for other manfacturers including the OEMs. There was a problem with the M-53A oil pumps locking up and shearing the teeth from the cam and oil pump drive gears. This caused further engine destruction due to lack of oil pressure. Be sure to disassemble any new oil pump, throroughly clean and verify clearances prior to installing - another problem are the gunked up/clogged original old oil pick-up screens that are near impossible to throughly disassemble and clean - just spend a few extra bucks and try to find a NOS unit along with a new O-ring and pick-up mounting gasket for the cast aluminum "L" shaped pick-up tube - plenty out there. If you can "pre-oil" the engine (prior to starting) by tapping into any of the oil galleys on the block that would be, in my opinion, mandatory as well. The FSM has all the operating clearances listed for verifying the new oil pump. Original cover gaskets will usually set the correct end play for the gears.

 

FYI, If you are ordering for a gear drive L or F-head, use M-53A - for an early chain drive L-head, use the M-53. The difference is in the helix on the oil pump drive gear caused by the rotational difference between chain drive vs gear drive on camshaft.