E: Engine Twin oil pump fitting

SteveO

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VOC Member
Hello all,
The rebuild of my 1951 Rapide continues at its snail pace. Having finally installed the main bearings after some fettling, I am now struggling with the oil pump. The old one was quite badly worn on the worm drive so I am fitting all new parts. Richardson says the pump sleeve should be a slide fit, however I have read elsewhere sometimes it needs the casing heating to get the old one out. This was my experience. I was hopeful that the new one would be a slide fit, but no such luck. After four attempts, leaving the sleeve overnight in the freezer and heating the case has allowed me to install it; it still needed driving in, which is a long way from a slide fit. Now, of course, the pump rotor won't go in. It tightens up where the slim end of the rotor enters the housing at the far end. The book says it may have to be replaced by different parts to ensure the correct fit, as the parts are paired.
Firstly, should it be so hard to get in? Other users experience welcome.
Second, what now? Once the case has contracted after heating, the sleeve is obviously now too tight. Presumably it will have to come out again. When it's out, am I likely to be able to select a better fit, or should I think about having about a thou taken off the OD? Or ream the housing or the sleeve in situ?
 

Peter Holmes

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Steve, I greatly admire your "have a go attitude" but I think that is a job best left to the experts, Maughan's springs to mind, but you might have to twist their arm to get it done quickly, it is quite a delicate thing and getting it out now could lead to distortion.
 

vibrac

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I have fitted them in the past I remember my worst fear was not getting the oil pump drive pin hole in the sleeve lined up. I am sure if you did the job on a regular basis its not too bad but as.a one off every five years it can be a Bas***d. The crank case needs to be really hot its not enough to spay it with a flame and hope.
Personallyfor me at this distance in time I would sub it out if at all possible certainly its a job better done with an unassembled engine.
 

Bill Thomas

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VOC Member
I bought a straight reamer to open out the hole in the case and did 2 Comets,
I think I blunted the reamer a bit first,
To try not to take too much out !!.
I would heat the cases to get the one out that has got stuck.
And see if the new plunger is still free in your pump.
It's tricky, If the case hole is too big, You will have sumping trouble !.
When you are happy, Check with the screw OP36 in tight that the plunger is still free to turn,
We had one where the Screw was too long and was stopping the plunger from turning.
Good Luck, Bill.
PS, I can't see the point of heating the cases, Because when they are cold it will make the plunger too tight,
Which is what you have had.
 

SteveO

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VOC Member
Ho hum. Peter, I've had it in and out four times precisely because the holes wouldn't line up as Vibrac says! The sleeve was twisting in the bore as it was driven in. I'm loathe to heat it up too much because the outer races of the mains are held in by Loctite and plates (Loctite 648, good to 175 C). Now it's in I'd prefer to leave it as the holes finally line up! Vibrac, you are right, getting it out is real good fun, you have to use a crankcase bolt in the extractor hole, then put something round it and hit it (mole grips in my case)! Strangely, it seems to foul where the sleeve is thicker - you would think it would be compressed more at the outer end where it is thin. It would appear however that my problem is not unique! What are peoples thoughts about relieving the plunger? It doesn't appear to under a lot of stress.
 
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SteveO

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BTW it took Maughan's several months to do the big ends, I don't really want to go back there again in a hurry!
 

Vincent Brake

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VOC Member
I always clean it out with a hone mandrel

Easy to make
Just a pice on brass or cast iron at 0.02-3 under sise.
Than some very fine abrasive powder oil and thats it.
Be sure to machine down the middle part on the sleeve whom is open.
As it can bend"" the sleeve when seated.

Than do the pump itsself with fine "Time saver lapping compound.

This will not Bed into the brass.

I dont hope your snail comes to a hard stop here.....
 

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
Another thing to consider is the linear rate of coefficent of thermal expansion for the different materials. Ignoring what the number actually means:

Aluminum = 22 approx
Bronze = 16 to 18
steel = 12 approx

This means bronze expands slightly less than aluminium so heating the cases to remove the sleeve will have a little effect but not a lot. Steel roughtly expands at half the rate of aluminium which is why you heat the crankcases when removing the mains bearings.
In use the sleeve and crankcases will basically keep the same fit hot as when cold, but the sleeve will expand a bit more than the pump plunger. This is probably why the factory said the sleeve can be a push slide fit in the cases.
Usually over the years the crankcases distort slightly so the 1" bore in the cases for the pump sleeve is no longer true down it full length, ie its slightly banana shape, and so the new sleeve distorts over its length when installed.

Simon
 

Bill Thomas

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VOC Member
I would have thought, If you heat up the case near the pump and get the sleeve out quick, Before the heat gets
Right into the sleeve, It would be better.
You really need a cheap slide hammer. Cheers Bill.
 

davidd

Well Known and Active Forum User
VOC Member
I have been lucky with most of mine. I usually test the bore of the oil pump chamber with the pump removed.
DSCN2325.jpg

I use a long 1" reamer. I have never had any serious trouble fitting one in a Comet case. As I rotate the reamer I might a a few minor spots that the tool will grab, but nothing dramatic. If I encountered a lot of resistance I would probably continue working with the reamer. However, I like Vincent Speets description of what he does as reamers can often gouge if you are not careful.

It sounds to me like the bore of your case has distorted. The oil pumps supplied by Mayghan have been built with an internal clearance that take into account that the bore might be very slightly distorted. Thus, if a Maughan pump sleeve is a tight fit on the worm, that tight fit is telling you that the bore needs serious attention.

It is not unusual that the sleeve is a tap fit, but it should be a very easy fit, not hard. I start the sleeve in a retarded position to its final resting spot and twist it clockwise (the direction of of the installation tool tightening and do it slowly to make certain that the I can twist the sleeve to the correct spot. I sometimes go to far, but the sleeve will come out easily. Test fit the worm. The oval hole usually has some burrs on it. Careful filing will usually fix it easily.
Tools 8.jpg

Tools 10.jpg

The cases will absorb an amazing amount of heat. I am with Bill. If you can get the cases warm you can then do localized heating around the pump to pull out the sleeve. You should not get the rest of the case hot enough to worry the Loctite. If the whole case is warm it will not draw away the heat around the pump sleeve so quickly. It is good to do this with all due speed!

David
 
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