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MG Midget and Sprite Technical - New Oil Pump Problem

I had a couple of hours to spare this morning, and decided to assemble the back end of my Frogeye engine: backplate and flywheel. I closed up the bottom end some time ago, and the engine's been sitting under an oily rag with tape over the various orifices.

I struck an immediate problem - the backplate won't fit over the oil pump. So I had a good look at the tin cup which covers the oil pump hole, and which in this case was soldered to the rear face of the backplate (I thought the last A-Series I built was cup on first, then backplate trapping it).

The cup was a bit off-centre, with lumps of solder in the opening, so I got out the blowtorch and detached the tin cup, and cleaned up the hole in the backplate. But it still won't go over the oil pump.

Here's what the new pump looks like.

It's fouling the backplate at the cross-head screw bottom left, and at the blank projection bottom right - that's with the backplate lined up on its locating pegs.

What would you do? Both foulings are about 1⁄16"



Nick and Cherry Scoop

1. yes the tin cover is supposed to fit inside the backplate (on 1098 & 1275s anyway, not 100% sure re 948s).
2. did you keep the old pump, a comparison might be revealing?
David Smith

Is there a rebate for the tin cup on the backplate inside face, on 1275s? I guess there must be, or it couldn't be 100% oil-tight. Anyway, there isn't a rebate on the 948.

Here's the old oil pump. Very compact compared with this new Mini Cooper one - or maybe it's Metro; Peter Burgess got it for me.

The old one's in good nick, but useless unless somebody is still using a pin-drive camshaft.

It seems the one thing I will definitely have to do is notch the backplate in two places - maybe also taking a wee shave off the two offending projections.

Nick and Cherry Scoop

Nick
What about countersinking the three holes and sustituting the three bolts for machine screws?
Alan
Alan Anstead

Hi Alan

The problem isn't the projection from the block face; it's those two lumpy turrets bottom left and bottom right.

You'd think the circular hole in the backplate would be the same dia as the sinking in the block for the oil pump, but it isn't.

BTW, here's the inside face of the backplate. No rebate for the tin cup.

Nick and Cherry Scoop

Nick
Can you get a later pump cover, cut off the lip, open out the backplate hole and solder it in. You would have to be carefull of height so that it did not tOuch the reverse face of the flywheel.
Alan
Alan Anstead

Here's one I stripped earlier.

Rear face of a 1275 backplate, complete with recess for the oil pump cover seal.

Lawrence Slater

Im with alan ...

If you only needing 1/16 inch .... I d get counter sink screws and pull out the 4 screws that are there, get a counter sink bit and re cut the screw hole and but in the counter sink screws with some red locktight.

Im guessing the current screws have a 1/4 inch to 3/8 inch tall head. So making them flush with the pump body would be the option id go

Prop
Prop and the Blackhole Midget

Prop you're not reading correctly. The interference is lateral (sideways) not outwards.
David Smith

Thanks, Lawrence. I didn't imagine it all those years ago.
Nick and Cherry Scoop

David...

Thanks... I didnt pick up on that
laterial... meaning it dosnt fit side to side

But the depth is fine ???

Hmmmm....interesting (while inhale sucking air between my teeth)

Prop
Prop and the Blackhole Midget

The reason for this is that this perticular type of pump is an adapted 1275 pump, which had a bigger body due to a larger 4 lobe rotor. And of course more capacity, which is why 1275s don't have their oil pressure struggle as much, especially at idle.

There is available a pump to the original pattern, complete with 3 lobe rotor, which does fit as original. We stock both types, but I'm out of town at present so can't check who our suppliers of each type are.

However, the adpated 1275 pump needs only a relatively small amount to be filed off the pump body (in the vicinity of one of the bolts IIRC, certainly in a place where it's not a structural issue) and it will fit under the cover. As the pump is higher capacity that the original, I have to say it's my preference. But we stock both types and have the above discussion each time someone orders a pump for a 948 or 1098 and let people take their pick.
Paul Walbran

Thanks very much Paul. It's reassuring to hear that others have met this problem. I will see if I can grind the pump body carefully in situ, though I will have a look inside at the turret thicknesses first.

If I need to notch the backplate as well, so be it. At least I know that the tin cup fits over the oil pump now, so it will be a question of :-
(i) grinding,
(ii) fitting the backplate,
(iii) locating the cup,
(iv) tacking it in place,
(v) soldering it properly with the backplate off.

Anybody see anything wrong with this?
Nick and Cherry Scoop

Nick, I think grinding anything in-situ is risky as grinding dust and fragments get get into places they really shouldn't. Filing in situ is marginally better as metal fragments do less damage than grinding fragments but, seriously, I'd do the job on the bench and then thoroughly clean prior to fitting.
Nick Nakorn

Bummer Nick, if you need anything doing come up and we will fettle it for you or maybe see if we can turn down the spare small block pump I bought in at the same time as yours and post it to you?

Peter
Peter Burgess Tuning

Good advice, thank you Nick. I decided not to do that.

Peter - what a kind offer. But, for better or worse, I've now notched the backplate in two places - only a sixteenth - and it fits! I found that the backplate hole doesn't correspond with the block sinking - not a different dia, just lower - so I'm wondering if Mr Derrington threw this engine together from bits.

The tin cup will now sit about ⅛" higher than before, and I've had to ease the flange a little to miss the bellhousing. Hooray! I actually thought ahead for once!

Now I just need to learn to solder.
Nick and Cherry Scoop

A case of solder and soldier on :)

Peter
Peter Burgess Tuning


Now I just need to learn to solder.

Marshmellows and hot dogs ... makes a marvelous threat waiting for the fireman to arrive

Prop
Prop and the Blackhole Midget

Nick, check the clearance to the flywheel before you get too far!
Paul Walbran

I've misled you, Paul. When I say higher, I mean towards the cylinder head, not towards the gearbox.

By the way - how do you solder a reasonably thin steel flange to a thick, hard-to-heat-up backplate? All the help on Youtube seems to be about wires.

I dimly remember making the usual tin cup in metalwork lessons 50+ years ago, but otherwise I am a real beginner.
Nick and Cherry Scoop

Are you any good at plumbing?

I did try to resolder one many years ago, but I don't think I was able to get enough heat into it.

You will need a HOT blowlamp. Hopefully a butane/propane mix will get it hot enough.

I would be tempted to 'tin' the flange of the cover first, put some flux on the backplate, clamp the two together and heat it up.
Dave O'Neill 2

personally... id use that LONG set time 2 part epoxy weld...24-48 hour cure time. Definatly none of that 5 minute stuff

Its not that I dont know how to tin and solder, its just I dont do it very often to be very good at it, and if that joint fails, pulling the engine and gear box (agian) is ALOT of work then having to stick it all back in...yeah no thanks .. ither "perma weld" or "Loctight" 2 part epoxy in a long cure and set time is the direction id go.

Probably not JB weld ither..theres better quality 2 part epoxy welds out there

Prop
Prop and the Blackhole Midget

Thanks, Dave. I did manage to get the whole thing hot enough to take the cup off, but of course any fool can melt solder.

Your suggestion sounds good, though. Do those crème brulée blowtorches produce a hot enough flame for local tacking, do you think?

Prop - that's worth thinking about. But I guess it's forever.
Nick and Cherry Scoop

I'd do what Prop has suggested but use JB Weld.

The canister doesn't actually have to be soldered does it, just to stop any leakage getting out onto the clutch side.

The pump body to block joint has a gasket on it.

Lara's canister is just popped into the hole and held by the action of can to engine casting by the backplate, there may be some Hylomar in it.

I broke the original cast backplate at the starter motor cut-away and had to buy a replacement steel one.

I remember having a hard time cutting the right shape at the back for the triangular bridge piece with a file.

Good call Prop.
bill l

Nick, what are you heating it with?

When I tried it, I was probably only using a butane blowlamp. I've since discovered butane/propane which seems to burn much hotter.
Dave O'Neill 2

"Do those crème brulée blowtorches produce a hot enough flame for local tacking...?"

Now why did I just KNOW that would be the only reason you owned a blowtorch, Nick? ;-)
Steve Clark

Ah - caught out again. You're so right, Steve.

Bill - there's a little crescent-shaped hole where the pump body meets the block, where oil can slosh through from the sump - don't know its function - so I do need the can/backplate joint to be oil-tight. And my can isn't trapped by the backplate against the block.

Like you, I do like Prop's idea, though. Now I just need to find JB Weld in the Welsh Marches.

My blowlamp is just a hobby one with a camping gas cannister, Dave. It melted the solder, but it would take ages to get enough heat into the thick steel of the backplate.
Nick and Cherry Scoop

Nick,

If the torch melted the solder to get the can out then it should be OK to put it back in. If all is still tinned then just clean it up, flux it with a decent flux, I like an acid paste flux, place the can in so it can drop when the solder melts and heat away trying to get the whole can solder joint molten at once so it settles and seals.
David Billington

OK Nick I'm sure you can get araldite there though

As it is not intended to start the engine straight away - I hope, you can use ordinary slow setting poxy for the job



sloshing oil

eeek - messy

I think you would need a local chap handy with an acetylene torch to reheat the backplate enough to resolder that huge lump of metal

is it steel or cast iron?
bill l

What about pre heating on a propane BBQ grill and an electric hair dryer/heat gun to help add oxygen to the flame from below the grill to raise the heat even higher... once maxed out, you can use your solder iron to finish off the temp and as david says, "drop the can into place when the tin melts"

One draw back.to the 2 part epoxy, would be the heat range... I want to say "perma weld is around 300 F. But I think JB weld is lower... but id think anything around 225-250 F. Would be safe, as anythng over 210 F is pretty much maxed out for engine temps

Prop
Prop and the Blackhole Midget

But....

Then agian.... what kind of temps are we talking about to do tinning and soldering... they aint exactly space shuttle temps, so maybe a long set run of the mill 2 part epoxy weld would be fine

Prop
Prop and the Blackhole Midget

A fairly easy to comprehend chart here for some basic solder types http://www.kester.com/kester-content/uploads/2013/06/Alloy-Temperature-Chart-15Feb11.pdf . I would trust a well done soldered joint long term more than an epoxied joint unless I really knew the details about long term oil and heat exposure to the epoxy as after all the original joint lasted 50+ years until it was attacked with a gas torch. Using adhesives can work well but in order to get a good lasting result you really have to pay attention to the surface preparation details. One adhesive I have used mentioned basic drying of the surface with a hair drier prior to adhesive use as invisible moisture on the surface could seriously effect the bond strength but gentle warming with the drier would drive the moisture off and ensure a sound joint.
David Billington

The JB weld brochure says 550F is OK; I wouldn't expect a hotspot there.

Also: "When fully cured, J-B Weld is completely resistant to water, gasoline, and about every other petroleum product or automotive chemical. "

Haven't decided yet.
Nick and Cherry Scoop

If it helps I have used JB_Weld to glue the magnet to my rear brake drum

Many kinds of other epoxy goo have given up the ghost in a similar time scale



.

The magnet is the rotation counter for my bike computer

Works a treat



(Next week it will fall off, now I have boasted about its capability)

:)
bill l

This thread was discussed between 23/10/2014 and 27/10/2014

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