oil pumps

I have 4 oil pumps in a box. Two have what I call a small body and two are a larger body, same bolt pattern. The seat for the conical oil seal is wider on the large body pumps. What is the history of these? One better than the other?

seattle##gs said:

I have 4 oil pumps in a box. Two have what I call a small body and two are a larger body, same bolt pattern. The seat for the conical oil seal is wider on the large body pumps. What is the history of these? One better than the other?

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They used a pump with a narrower body and narrower gears on ealy engines without full pressure oiling to the head.

They used a pump with wider gears and a small seat for the conical washer on Commandos except the Mk3.

The pump used on the MK3 had wide gears and a larger seat for the larger conical washer.

The washer seat can be exchanged between pumps as it is just a snug fit in the body. Jim

"The washer seat can be exchanged between pumps as it is just a snug fit in the body. Jim"

The vast majority of early pumps MUST be machined with a larger flat spot or the MKIII seal holder will NOT sit flush on the older pump bodies.
Early seal holder on a late pump is no problem.

"snug fit" OK..... I had to make a tool and need to dismantle the pump to press out the seal holder. Otherwise you might need a collet type of holder to get a good grip for the pull. Butchery and damage to seal holder is otherwise possible DAMHIK