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E: Engine Twin oil pump fitting


SteveO

Well Known and Active Website User
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
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

Well Known and Active Website User
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.
 
Last edited:

SteveO

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
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.....
 

vin998

Well Known and Active Website User
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

Well Known and Active Website User
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 Website 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
 

vibrac

Well Known and Active Website User
VOC Member
get some allthread or some round bar put a thread for the end of the pump (5/16)"? get something heavy with a hole in the middle for the bar slide it on the bar put a nut on the far end and you have a slide hammer
if its man enough a couple of slides to the end and out she comes!
 

oexing

Well Known and Active Website User
VOC Member
While reconstructing my Argentina B-Raps I had to deal with same problem a few months ago and decided to get a real nice push fit at NO resistance at all for fear of distorting the delicate sleeve. After checking the bore for nicks and dents, you can run down a reamer if you got one, provided it is not blunt at all, and if still not lucky to push the sleeve in to its stop, you could smear some extra fine abrasive paste up the bore and use the brass sleeve itself for lapping it up the bore. I got paste of 5 micron , diamond or the like and screw the sleeve on the end of a threaded rod for manipulating it up the bore. Just see that the paste stays up the bore mostly so you don´t enlarge the bore at the entrance too much. Sure, you get a tiny taper along the bore and sleeve at the top but I do not think it is critical or a negative factor when located in its final position. When up to the stop there is only minimal play in the assembly and wet sumping cannot be a factor after the engine has cooled down and oil got its high viscosity again. So no real need to go for a press fit, too much risk of getting a seizure when knocking the sleeve in and insufficient running clearance for the plunger. Just keep the rear part of the sleeve clean of paste and most of the honing action in front of the sleeve, manipulate the lot in a honing motion with paste and oil, cutting oil is great.
In case you have to remove substantial material in the bore and your blunt reamer is unable to free cut to size you are entitled to use a secret toolmaker´s trick for restoring the reamer to achieve an individual size. You get a piece of carbide, like a lathe tool insert or a rod of carbide and run it along the cutting edge of the reamer under an angle like in my photo below. That way you create a tiny burr along the flute and so will be cutting the bore to your liking. Be cautious with forming these burrs, you can set the reamer to oversize two or three thou with this trick. You can check with your finger nail at the reamer edge for "size" .

Vic
P1050789   Paint.jpg
 

SteveO

Well Known and Active Website User
VOC Member
Thanks for the replies.
OK, I need to do some thinking out loud now. I have the pump sleeve in now and in correct alignment, I don't (really don't!) want to have to take it out again. If the housing is distorted, reaming it out is going to take it oversize somewhere, so there is a possibility of leaks or loss of oil pressure? I'm not quite clear what Vincent is suggesting, is the honing to the sleeve or the housing, or is it both? It's a bit late for the housing in my case and even if I were to pull the sleeve out again and do it, it may distort again when it goes back in leaving me where I started. There appears to be some damage to the housing around where the outer main is driven in, I wonder if this is the source of the distortion? It would make sense if the housing is out of true that the plunger won't go in, but if I ream the inside of the sleeve I would have to be dead accurate or oil will be able to get past the plunger affecting the oil pressure which I don't want! Is this correct? Or does it matter with the nose of the plunger, as this doesn't appear to transfer any oil. It's nice to know that warming the cases won't affect the Loctite as I don't want to have to go through all that again.

"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. "

Vincent, can you please advise on "abrasive powder oil", I'm not familiar with the term. Is this carborundum oil such as used to be used for running in? When you say machine the middle part do you mean concentrate on this section as it distorts when fitted? Is "time saver lapping compound" what I would know as valve grinding paste?
 

tatty500

Well Known and Active Website User
Non-VOC Member
Twenty years ago when putting my B back together, after 30-ish years in bits, I was worried that the big race of the new big main bearing had not gone properly home.

To be certain I tapped it a bit with a hammer and soft drift.

It was only later when I was looking at that cross section of the engine at about page 18 of the riders handbook that I spotted how thin the crank case is between the bearing outer and the pump bore. I think this was why my original pump on being refitted had a tight spot.....Silly me.

However, when it came to getting the pump sleeve angularly in the right place I found that a smooth ended rod of the correct diameter for the scavenge/return holes in the sleeve could be inserted through the 1/4BSP return banjo hole and used to rotate the sleeve to the correct final position....assuming its not a mile off to start with.

PS don't forget to check that the OP36 screw is not too long if you are fitting a new one.

Best of luck
Tatty
 

Bill Thomas

Well Known and Active Website User
VOC Member
I am trying to remember, There is a small bit of crankcase that is very thin and can break away, Right next to the pump sleeve / Main bearing, Not a problem, As long as you see it and remove it.
 

Vincent Brake

Well Known and Active Website User
VOC Member
The abrasive powder oil, is bad endlish for:

Time saver lapping compound.
I use it where diamond or SiC can bed in thus creating rapid wear.
Trick with this stuff: it goes blunt rather quick, loosing its sharpness.

I buy it in the Trump country.
And use them with Acro expanding mandrels.
Really was an eye-opening item.
Thought i heard it from DavidD.
 

Vincent Brake

Well Known and Active Website User
VOC Member
On the brass part i do machine the open part , (where the worm engages with pump) an 0.1mm down in daimeter. No need to lay stiff to the casing there, causing possible distortion.
Hence better fit for the pump itself.

But as you said
I DON'T TAKE IT OUT.
To late in my reply, sorry
 

SteveO

Well Known and Active Website User
VOC Member
Right, I've got the sleeve out again, reading the comments above that seems to be a no-brainer. Bill, you are quite right, the heat makes no difference, it drove out just the same cold. I now find the plunger still won't go in, so does this mean I've scrapped £300 of pump? SWMBO will not be impressed! I've enclosed some photos. Bill, you are right again about bit of crankcase breaking away (not by me, a PO!). One of the photos shows how far the plunger goes in without jamming - about halfway, which would support the notion that the sleeve has bent in the middle. Doh!
 

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