oil pumps

[wilko]

How much different are  unit and pre-unit oilpumps? Never seen a unit version? There's are late cast iron unit one on ebay? douglas.

[Goldy]

As far as I am aware they look the same but the unit ones are slightly longer and will not fit pre unit.
Regards Goldy

[trevinoz]

I'm pretty sure that you can fit the pump section to the A7/10 drive section.

 Trev.

[beezermacc]

I seem to remember the worm drive is cut to turn in the opposite direction. Somebody correct me or confirm this please.

[trevinoz]

The A65 pump does rotate in the opposite direction to the A10 but the pumps themselves don't care which way they rotate as they are gear pumps.

  Trev.

[KiwiGF]

I'm interested in this also as I have 4 original "alloy" pumps all of which have faults to one extent or another. The SRM pump is a bit pricy and the A65 pump seems a good alternative if not as good, as I think I read somewhere it has 30% wider gears like the SRM pump.

Reading the above would I be right in concluding:

1. To use an A65 pump you MUST fit a different drive end on it, and the A10 pump drive end will bolt straight on, no problems?
2. The A10 "drive end" includes the part of the alloy case the "cylindrical" gear rotates in, and also the gear?
3. The A10 crank worm gear MUST be retained? (to mesh correctly with the A10 drive end)
4. An A65 pump fitted in an A10 with an A10 drive end will rotate the opposite way around to how it will rotate in an A65?
5. An A65 pump rotating the other way around in an A10 will pump oil the correct way around an A10?

Thanks

(subject to confirmation a bloke I know who has lots of new A65 pump parts is going to get a call from me....)

[Goldy]

I think you are on dodgy ground fitting parts from one used pump onto another used pump. The tolerances on these pumps are very fine for obvious reasons and fitting the end plate from one to another will result in either a tight fit or too much clearance which will result in loss of performance.You say the SRM pump is too expensive, but what is the value of you machine in a seized condition.

[kommando]

The way the oil pump works changing end plates will not affect anything, they are meant to be flat and as long as the new one is flat they will work. When I recondition a pump I put grinding paste on plate glass and remove all of the wear marks and get full contact over the full surface so its flat. The critical item is the gears, they were fitted in matched pairs so where possible keep the gear pairs and if possible together with the body they were fitted to. To be safe have a temporary port to test the pressure produced by the pump on a running engine.

[beezermacc]

Regarding the gears, as mentioned by kommando, some gears have petal shaped teeth, others have triangular teeth.

[KiwiGF]

Thanks Kommando, sounds promising, the a65 pumps I have in mind are new or at least almost new.

I will also devise a rig to test the max pressure versus a STD pump.

I guess all the answers to my earlier questions are "yes" then?

Re the gears I've got a brand new set and some old ones and I can see the difference in tooth shape.

[jmatch]

Late addition to the discussion but here are the two oil pump drive gears, A65 on the right, A7 A10 on the left

[kiwipom]

hi guys, some pump pics showing differences between A65/A10, cheers

[JulianS]

The late cast iron A65 pumps were the best. Apart from the improvements of the dowelled body and o ring in kiwipom's photos they were fitted with gears with 11 teeth which were slightly wider.

Similar gears fitted in my SRM pump - the feed A10 gear being about 0.3 inches wide and the SRM about 0.34, the scavenge A10 gear being about 0.44 wide and the SRM about 0.58 wide.

Unfortunately did not photograph them but the photo attached shows the cast iron SDD (Stuart Digby Developements) A10 pump produced in the mid 1990s with similar gears. Nice piece of work.

[chaterlea25]

Hi All,
In the second pic from the top in Kiwi's post
You can see the two different types of gears "mated" together in the lower pump 
15 and 14 teeth

a recipe for mechanical marmalade 

Recently I have been fettling a pump for my GS "special"
I am using NOS gears and a new cast iron body, and a phosphor bronze drive end plate
It has taken many hours to get it running anyway smoothly, and more to go 
Singles will destroy the worm drives to the pumps if the pump is too tight

Personally I wont risk an old mazac pump on an A10 engine 
I have seen oil leaking through the mazac (monkey dung) bodies 

John

[JulianS]

My feeling also re mazc.

I think the 15 tooth gear is early type which was changed in 1956.