A65 Oil pump diffences

[Bess]

I putting together a couple of A65's and have checked assembled 2 oil pumps. A 1960's the other 1970's, the 60's pump has a counterbore in the non return valve ball location.

Please see attachment

My research has found the valve spring is the same for all years so I guess the counterbore has little effect on the pump function.

Is there anything I need to be aware of due to this difference?

Thanks for looking.

[TTJOHN]

I think this was most likely done to fit a small 'o' ring, I could be wrong but I think that's what it was meant for, I seem to remember seeing one fitted to a OI frame A65.

[Bess]

Thanks TTJOHN.

I am not to sure about the O ring as its not listed on any parts list. Interestingly it's the older pump that has the counterbore, not the 70's possibly OIF model which has the bulkier castings around the stud holes.

[Bess]

Sorry, when I wrote older I ment the 70's pump....

[AWJDThumper]

I would assume it's there in order to provide a wider sealing surface for the NRV 1/3 ball bearing. The mod compared with earlier pumps may have been to make the sealing more effective?

[AWJDThumper]

Sorry, 1/4" ball bearing 

[JulianS]

The countersunk hole is mentioned in the A65 workshop manuals.

Parts service bulletin G39 from February 1967 shows an improved A65 pump, amongst the changes was that the A10 body 67 1382 used until then (which was not countersunk) was changed to a new part 68- 934. Could be that the countersink was added at this time.

One of the A65 blue top service sheets recommends that the ball is seated to a new alloy pump by tapping ball to pump with a copper hammer.

[Bess]

Thanks guys.

It all makes sense however the earlier pump (60's) has the counterbore, the 70's pump does not.

[JulianS]

When my A10 was converted by SRM some years ago the pump came back with such a countersink added.

The cast iron OIF pumps were ground in that area to seat the ball,

[TTJOHN]

Bess, I did get it wrong, I remember now the small 'o' rings were on the oil pipe flange, where it fixes to the engine body. Sorry

[Bess]

Thanks TTJOHN,

After reading the replies (thanks all) I decided to counterbore the pump. I then silver soldered a 1/4 ball on a mandrel and lapped in.