SRM Replacement Oil Pump

[duTch]

  I don't have an SRM pump, but as GB said .
 

 ........................ You will receive new Allen bolts in place of the studs along with an installation sheet. .....................
Regards
ELLIS

     

 ....I stuck socket cap screws in for convenience, but have learned better and ( when I get some), want to replace them with original studs for better torque-down / anti-loosen / thread protection effect

[rowan.bradley]

want to replace [socket cap scews] with original studs for better torque-down / anti-loosen / thread protection effect

Why are studs better in these respects? If they are, why do SRM supply socket screws?

Thanks - Rowan

[KiwiGF]

Photo shows the gears used in the late A65, SRM and SDD oil pump. Scavenge gear much wider. All gears have 11 teeth compared with 14 on the 1956 on A10 pump so move more oil.

The SRM pump is a proven product from a well known, reputable and easily cotactable dealer.

Hi Julian, on request, I gave a couple of pumps I intended using to my engineer guy to assess (local brit bike expert) and who did a lot of work on on my 56 engine, he told me to use the one that had new A65 gears and the same flow as an SRM pump, I did not question him on this further, but to me both the pumps looked identical from the outside. I assumed, possibly incorrectly, that it was the tooth size (not necessarily width) that provided a higher flow rate.

Am I wrong in thinking this? Is the A65 pump different in other ways than just the gears and drive end? (I’ve not seen an A65 drive end, but I’ve read it’s different because the pump rotates the other direction to an A10).

[JulianS]

It is much easier to remove and replace the pump using socket cap screws.

It is not usually possible to remove a pump held with studs and nuts without removing the pump drive worm from the crankshaft at the same time as withdrawing the pump.

But as always it is a matter of personal preference.

[JulianS]

The A65 pump was subject to a number of changes over the years.

The first ones used the A10 main body, 67 1382, (but nut drive end) and the same set of gear - feed gear 67 1403 and 67 1404 - scavenge gears 67 1405 and 67 1406.

By 1968 it had gained an o ring at the drive end and a different body but kept the same gears.

The shaft closest the crankcase joint was extended into the drive end.

Then the bodies were changed and dowled together for better alignment.

By 1970 it still had one A10 feed gear 67 1404 and one A10 scavenge gear 67 1404. But the same tooth form and nuber would have been used by the replacement or it woild not have fitted together.

So to this point the gears were the same although some improvements were made to the body which no doubt made a better pump.

Then came the cast iron oil in frame pump, a much better pump altogether with wider gears and fewer teeth and no chance of distortion by age or bad fitting or over tightening.

The SRM pump is a quality item and I am very glad not to be running a zinc alloy bodied pump.

On this pump as said earlier the gears have 11 teeth rather than the 1956 pump with 14, the feed gears on the SRM are about 0.34 inches wide compared to 0.31 on the A10, and the scavenge gears on SRM pump 0.58 inch wide compared to 0.44 on the A10.

I first used a high delivery pump on the A10 in 1994 when SDD produce a super cast iron bodied one and have never looked back being confident that the engine was getting the best oil circulation and pressure possible.

[a10 gf]

It is much easier to remove and replace the pump using socket cap screws.

It is not usually possible to remove a pump held with studs and nuts without removing the pump drive worm

Unscrewing studs is possible, see removing it and pump goes right out, at least works on my engine, studs not overtightened + good threads.

want to replace [socket cap scews] with original studs for better torque-down / anti-loosen / thread protection effect

Why are studs better in these respects? If they are, why do SRM supply socket screws?

imo...

Socket screws very practical vs studs very safe for threads (usually goes longer in, & thread strip over time will be located on nut side, not 'inside' the engine).

That said, if threads are excellent and it's parts that are not going to be removed \ refit for very long intervals, socket screws should work fine, probably why it's in the SRM kit. For removeable \ service parts like oil sump, I'd definitely stick to studs...

[Rex]

Yep....poor engineering practice to replace studs and nuts with screws/bolts....

[rowan.bradley]

Am I right that the argument against using screws/bolts is that you will be repetitively screwing a steel screw into an alloy tapping in the crankcase casting, whereas with a stud you will be screwing a steel nut onto a steel stud? And that if the nut or stud gets damaged or the thread strips, you can remove the stud and fit a new one, whereas with the screw you would be into helicoils etc.

Sounds reasonable to me. But I hope that once I've changed the oil pump I will very rarely need to remove it, and this seems to be confirmed by the people who have used the SRM pump and say that it is "fit and forget". So I don't think this is a big issue for me...

Thanks for all the advice - Rowan

[bsa-bill]

So I don't think this is a big issue for me...

no - sometimes very very best practice is just not as practical as easy practice (been talking to Confucius )

[Greybeard]

Am I right that the argument against using screws/bolts is that you will be repetitively screwing a steel screw into an alloy tapping in the crankcase casting, whereas with a stud you will be screwing a steel nut onto a steel stud? And that if the nut or stud gets damaged or the thread strips, you can remove the stud and fit a new one, whereas with the screw you would be into helicoils etc.

In the case of an oil pump it's not going to be disturbed very often so I can see an advantage of socket head screws in that they would make removing the pump easier. In other situations though, particularly the super-dooper drainable sump plate sold by SRM and others, socket head screws are supplied. This doesn't seem very sensible to me; the sump plate is likely to be removed fairly often and the socket screws can so easily be overtightened into your precious crankcases.

A tip if fitting one of these thicker sump plates that also have two gaskets with gauze between is to use the studs designed for the rocker covers. They are Whit one end and BSC the other and are a bit longer.

[RichardL]

When I was first rebuilding my A10 (OMG! 13 years ago, now) I was not aware of a lot of best or smart practices. When I checked the threads for my sump plate, three were bad and one was good. I fixed the bad ones with the most available solution, that is, metric Helicoils, and left the one remaining original Whitworth. I use socket-head screws and, to this day, have to keep track of which hole gets the Whitworth. I tighten that one with less enthusiasm.

Richard L.

[Sluggo]

The part about too fast oil flow is TRUE,, tons of engineering papers on this. (SAE)  Oil is a coolant and a lubricant.  If it flows too fast it does not pick up the heat or do the whole heat transfer thing it is supposed to be doing.  In addition, too fast is more friction.  Basic physics that shows the whole energy thing for every action there is a reaction.  Forcing a liquid requires force and energy, forcing it faster requires more.
But when you over pump lubes then you break down all the additives as well as Aerate the oil which is never good.  Oils ALSO have an optimum temp range.  (That in itself is a complicated topic)
Oil is very much a goldilocks situation.  Engineers calculate all this out for a design.. We can argue this all day but its pretty self evident that the oils BSA had in mind back in the 1950s is an entirely DIFFERENT concoction today.

The SRM pump seems to be a nice piece of kit, but for many of us is painfully expensive.  I have been intrigued by the idea of alternate fittings and was planning to research the late model A65 pumps for retrofit.  I have a few late model cast iron A65 pumps as well as the crappy alloy early A65 pumps and thats a future project.  I can snap some photos if helpful, but I dont have any A10 pumps handy at the moment.

In researching the A65 pump I ran across this page, and found it very informative.. well worth a look,
See: https://www.classicbritishspares.com/blogs/news/the-bsa-a65-oil-pump-journal-1962-1972

Pix, diagrams and text on the 3 types of A65 pumps on that page,,, here is what they say about the castiron pump.

" The BSA cast iron oil pump. Also known as the best oil pump and the rarest of them all. What makes the cast iron oil pump so sought after is the material in which it is made from. The earlier oil pumps before mid 1971 where made from a "pot-metal" alloy type material which is prone to wear and tear. I am not sure why it took BSA so long to develop a better quality oil pump. For those who own BSA unit singles, you will also notice that the 1971-1972 models had cast iron oil pumps installed. The problem with the cast iron oil pumps are, is that they are rare and expensive! The only alternative to the cast iron oil pump is going with a SRM oil pump. The cast iron oil pump can be fitted to all BSA A50 and A65 models from 1962-1972 and is the best upgrade in my opinion."

[Colsbeeza]

Hi Sluggo,
Something does not ring true to me about heat transfer . As flow increases, the heat transfer rate increases to a small power (roughly 0.23 if I remember correctly). That means that the fluid transfers heat more rapidly. So the temperature difference from inlet to outlet is lower.  Perhaps that is what you meant? The recirculating oil would average about the same temperature overall, as it is governed by the rate of heat transfer to the environment. eg. an original oil pump may see an increase of 50 C Degrees, but the SRM may see 35 C Degrees due to higher flowrate, and the oil tank temperature would be about the same as before or slightly higher due to the extra friction you mentioned.
Your other points eg, aeration etc. seem quite valid.
Do you have references to a couple of papers to clarify this.?
Seems from your argument that the main benefit from an SRM pump is better oil flow consistency and reliability, not increased oil flow.
From my readings, the presence of oil is more important than the oil pressure in plain bearings. Not sure if I can find a reference to that though.
Important to me, as I am contemplating purchasing an SRM pump or something reliable. However, if I win the lottery, I may be better getting a cast iron original. Do they fit the A10?
Yours was a great contribution to the subject.
Colin
 

[Sluggo]

Hi Sluggo,
Something does not ring true to me about heat transfer . As flow increases, the heat transfer rate increases to a small power (roughly 0.23 if I remember correctly). That means that the fluid transfers heat more rapidly. So the temperature difference from inlet to outlet is lower.  Perhaps that is what you meant? The recirculating oil would average about the same temperature overall, as it is governed by the rate of heat transfer to the environment. eg. an original oil pump may see an increase of 50 C Degrees, but the SRM may see 35 C Degrees due to higher flowrate, and the oil tank temperature would be about the same as before or slightly higher due to the extra friction you mentioned.
Your other points eg, aeration etc. seem quite valid.
Do you have references to a couple of papers to clarify this.?
Seems from your argument that the main benefit from an SRM pump is better oil flow consistency and reliability, not increased oil flow.
From my readings, the presence of oil is more important than the oil pressure in plain bearings. Not sure if I can find a reference to that though.
Important to me, as I am contemplating purchasing an SRM pump or something reliable. However, if I win the lottery, I may be better getting a cast iron original. Do they fit the A10?
Yours was a great contribution to the subject.
Colin

Oh good lord, sweet Jesus, Mary & the orphans thats a mine field right there,, (another oil debate...  )
But I stepped into it.,.
So, what you are talking about has so many variables its possible to go in a lot of directions without strictly defining the exact conditions you wish to look at variables for,

Viscosity? Friction modifiers and additive content? Surface condition IE: Smooth or textured? Differentials in temp of the liquid vs surface? Those just come to mind, I am sure a full engineer could come up with a ton of other possibilities.  (I am only smart enough to be dangerous, dont claim to be a genius)

But this page might be a good start but you can read a LOT of articles just to get a nugget, but some are spot on.
See: http://topics.sae.org/heat-transfer/papers/

Fluid dynamics is a complicated topic,, but this looks fun!
See: http://papers.sae.org/2017-24-0041/

" During gasoline direct injection (GDI) in spark ignition engines, droplets may hit piston or liner surfaces and be rebounded or deposit in the liquid phase as wallfilm. This may determine slower secondary atomization and local enrichments of the mixture, hence be the reason of increased unburned hydrocarbons and particulate matter emissions at the exhaust.Complex phenomena indeed characterize the in-cylinder turbulent multi-phase system, where heat transfer involves the gaseous mixture (made of air and gasoline vapor), the liquid phase (droplets not yet evaporated and wallfilm) and the solid walls. A reliable 3D CFD modelling of the in-cylinder processes, therefore, necessarily requires also the correct simulation of the cooling effect due to the subtraction of the latent heat of vaporization of gasoline needed for secondary evaporation in the zone where droplets hit the wall. The related conductive heat transfer within the solid is to be taken into account.In this work, a preliminarily validated spray model is specifically implemented by solving the strongly coupled heat and mass transfer problem describing the liquid and vapor phases thermo-fluidynamics after impact and the wall change of temperature. The discussion is made considering a different boundary condition with respect to standard simulations. Sprays are assumed from to different injectors in order to verify the wallfilm simulation model: the impact over heated walls of the ECN “Spray G” is first discussed, by comparing numerical results with experimental measurements deriving from a combined use of the schlieren and Mie-scattering techniques, then the footprint on the wall of the spray delivered from a 6-hole Bosch injector is related with infrared thermography and LIF measurements taken from the literature."

This is another example,,,,
See: http://papers.sae.org/2016-01-0197/

" Prediction of Engine Thermal Behavior during Emission Cycle Using 1D Four Point Mass Model"

There are forums for specific engine design discussions and you can delve very deep into these topics,, Once you get into arguments with engineers things get very pedantic quickly....

[muskrat]