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MG Midget and Sprite Technical - Breather system routes

I am trying to get a good 'active' breather system set up on the engine in frog. The engine is one I bought from Nick Veuger, if anyone remembers him. Its fine itself, but its breather system was incomplete so I need to concoct something. Up to now it's just been an ambient pressure drain that drips into the floor.

I am a keen believer in the negative crankcase approach. I have a pcv valve atop the manifold to provide the suction and am trying to sort out a pipe connection to the front tappet chest. At the moment that has a simple draught tube going straight down. I joined a long breather hose from that back up to the pcv.

That worked well enough initially but then I realised by going down and back up again it created U bend that oil drains down into causing a sump effect in the pipe so it doesnt breathe. And worse it probably would cause a fairly spectacular AOSE if sufficient suction was applied.
(Anam oil suction effect)

Next refinement may be to cut the existing pipe near to the tappet chest cover and fabricate a new connection going upwards so that any residual oil in the pipe drains back into the tappet chest. But space is tight round there and it will need to find a route between exhaust manifold top water hose and carb heat shield.

All doable, but its always best to check what the original solution was! So how was a breather connection done pre appearance of the timing case canister?
GuyW

Guy,
Before a breather was put on the timing case, it was located on the front tappet chest cover.

Repro covers with the breather we’re available from Moss, they might still be? The torque setting for the covers bolts is incredibly low, about 5ft/lb, which is virtually finger tight.
Philip Sellen

Philip, I had looked at the rather generic Moss diagrams and I could only see the vertical down pipe type of breather on tappet chest cover engines. Were none of the tappet chest covers connected to pcv on the top of the inlet manifold?

I suspect I need to fabricate my own pipe connection that avoids the exhaust manifold, but doesn't go down.

The alternative would be to source a later style chain case with canister.
GuyW

The 1098 breather looks a lot like this item, although it’s not oriented correctly in the photo.

It may even be the same part.

https://www.ebay.co.uk/itm/334458307110




Dave O'Neill 2

AOSE Anam oil suction effect

🤣🤣
anamnesis

Dave, thanks. That's an idea although that particular mini version one looks like it would foul the exhaust manifold.

Another possibility is to take a downwards hose from the existing breather, and go via a sealed oil catch tank which would provide the break in any oil column which might develop, and that would prevent AOSE.
GuyW

Another thing I discovered, is that there are two sizes of tappet chest covers. Of course I ordered the wrong sort of gasket for the 'other' size! 😂
GuyW

Guy

The exhaust ports on a Mini are in the same place, so I would think it should clear the manifold.

Does anyone have a photo of a 1098 Spridget engine, I wonder?
Dave O'Neill 2

Google MGmidget engine bay, then scroll down to a red 1964 examply, Bains Classic Motor House. Breather hose appears to go to the side position.

Of if still unresolved I will have a look at the one in the workshop once I get over covid...
Paul Walbran

Thanks Paul. I couldn't find that photo, - I think google tries to be too clever, adjusts for different Coreolis force and shows me a different selection where I am.
But I think I have it sorted. Or at least I have a Cunning Plan. It just needs executing! 😂
GuyW

Hopefully this image will load.
Philip Sellen

Thanks Philip.
That must be a canister directly off the tappet chamber cover - a bit like the mini one that Dave linked to.
GuyW

Yes it is, off the front chest cover. That’s an original as it’s got a couple of ring grooves across it.

Moss have sold them in the past, don’t know if they still do.
Philip Sellen

I tinkered around with various breather systems in an attempt to cure the rear oil leak. I intially fitted a hose from the chain cover to one of the air cleaners but this didn't work so bought a PCV valve and hooked this up to the chain cover hose. The oil leak stopped but this could have been due to me ditching the absolutely useless lip seal conversion. However I started to get clouds of smoke from the exhaust and initially thought a piston ring had failed. Eventually I found that the chain was splashing oil into the cover outlet and the PCV valve was sucking this into the engine. I had blocked off the pipe on the tappet cover and made certain the dip stick was a good fit. I then rerouted the pipe to the tappet cover and and blocked the outlet from the chain cover. The system works perfectly.There is no drip and no smoke from the engine. My engine is a 1275 with a vernier timing chain set up. There is no baffle in the chain cover and I don't know if there was one originally. The oil catcher tank on the outside of the chain cover does have wire wool inside.

Jan T



J Targosz

I have the standard 1098 front tappet cover with oil separator. This is connected to the suction port on the HIF44 carb, without PCV valve. Only a very occasional drip on the floor. But on this engine I have ditched the totally useless lip seal conversion and had the rear bearing cap and half moon machined and line bored to original clearance. Expensive but it works. I am not sure the PCV valve is the way to go any more.
Les Rose

The suction port on the HIF44 and later HS carbs creates pretty much equivalent conditions to the pcv, so are functionally interchangeable. But so much simpler.

This thread is drifting into themes of the infamous oil sucking thread 😂😂😂. Who could forget the unnammed-one's brilliant video of the clear-fronted timing cover filling with oil. It certainly showed what was happening.

But it is a real issue.

On pcv and oil leaking, we have retrofitted a pcv to the XPAG engine several times with excellent results. The first one was a recond engine still dropping a 6" puddle after engine-off, which we were asked to investigate by the reconditioner (who was 400 miles away and the customer had since moved). We found the oil control housing to crank clearances double what they should be. A friend had told me of his successful experiment fitting a pcv, so I offered it as worth a try, which both parties were happy with. Despite the clearance issue the results were great, only a thumbnail of oil drip.

Jan, I am really interested in your solution. We have a car with the infamous oil sucker problem in the workshop at present: after 5 min running a massive smokescreen for a couple of minutes, then clears. Doesn't happen once the breather is disconnected. I have been scheming on half a dozen ways at varying cost to fix/control the existing breather, but the 101 solution of relocating the breather has been off-radar till now! LOL. I plead in mitigation that I didnt rush in and spend buckets of money on a complex solution without having a good hard think first, and the iterations have been getting progressively simpler and cheaper. This is simplest and cheapest!
Thanks for stating the obvious, I will dig out a vented rocker cover and report.
Paul Walbran

Hi Paul,

My problem was exactly as you describe. So much smoke from the exhaust that you couldn't see across the road. I took the cap off the PCV and it was flooded with oil. I tried organising the pipe from the chest oil catcher to have a vertical section hoping oil would trickle back but the suction on the engine was too strong. The PO had a vernier, duplex sprocket fitted to the cam and I wondered if a baffle or something similar had been removed from the cover to provide more room. I think the outlet in the tappet cover is protected by a baffle though.

Jan T
J Targosz

Hi Jan, oil sucking is a legendary problem on the BBS. Debate and speculation ran past 600 posts as I recall. The video I mentioned above is no doubt in the archives and worth a look. It shows oil entering the timing cover faster than draining out, the level building up as a result until it reached the breather hole in the cover, so entering directly into the breather system.

I had an interesting discussion with my customer today. He reported that there was no issue originally, then #3 rings broke up, started burning oil and when re-ringed/new pistons the general oil burning stopped and the dreaded oil sucking reared its head. I am wondering if sludgy deposits, of the type that form when burning oil heavily, have restricted the drain holes between timing cavity and the sump.
Paul Walbran

I should have known this thread would drift off down the slippery slope of oil sucking!

But back to my tappet chest breather connections. On my engines (948 & 1098) these covers are held in place by a single bolt, which is quite awkward to locate through the cover. I've ground a pointy end on the bolt which helps it align and get started, but wondered if they ever used a short stud, with nut and washer? It should make assembly easier.
GuyW

My original 948 engine from the frog had a tapered lead in on the two tappet chest bolts. They looked like a factory application. Your idea seems even better.
Bob Beaumont

Grr! I'm still struggling with this. I had hoped to get a front tappet chest cover on my 1098 engine as in the photo that Philip posted. I then went ahead and bought the mini item on eBay that Dave linked to as it quotes the same part number as Moss has for the 1098 front cover - 12A1212. I even went ahead and repainted it.

However, trying to fit it it fouls the top coolant hose, or, rather it comes up against the branch for the heater pipe. It looks like the cannister part is canted forwards too much. I cannot see any way around this - not using that part. I could just order another from Moss, but as it has the same part number as was quoted for this mini one, I guess it would be the same?

Can anyone shed any light on this? Are the part numbers being listed wrong?

Sorry, 2nd photo insists on appearing upside down, whichever way I rotate it before linking!






GuyW

How's this look?


Martin

Yep, that's better Martin. Weird though. If the original was the right way up, BBS showed it upside down. So I rotated the original therough 180 degrees - and BBS still put it upside down!

Anyway, your version does show that the canister part is tilted too far forwards, maybe by about 25degrees. View is foreshortened a bit; the canister is reasonably clear of the exhaust manifold
GuyW

I don't have access to a parts number list. Is this 12A1212 correct for the 1098 engine. Moss seems to think so. They also list that same number for the 998 Mini, which is what the one I bought was listed as. Same part number.
GuyW

Guy,

This may sound too obvious but when you rotated it, did you "save" it before downloading?
Martin

I think we have one at the workshop which was removed from a 10CC engine, provided memory fade doesn't kick in I will dig it out.
Wondet if B series one would fit? May have to reposition the pipe, but would be easy to do.
Paul Walbran

Not much help I’m afraid, but as I recall from about 15 years ago, the repro units were made at a different - not such a convenient - angle than the originals. But it still fitted within the allotted space.

I don’t know if the mini version is the same as the MG/AH version. Seeing that the engine placement in the engine bay is different then I can well believe they could be different.

I’d suggest a call to Moss for clarification Guy.
Philip Sellen

It clears the exhaust and I think will just about clear the fatter top hose. But it is stopped by the smaller heater branch, just below the jubilee clip in my photo.
But in that photo that Philip posted earlier, the canister itself looks like it is very nearly vertical, whereas mine is tilted forwards. And that, obviously, is with the tappet cover itself aligned properly even if it won't go tight into position against the engine.

That's why I'm asking about part numbers.Is it possible for two variants of the same part, with differences, to still have the same part number?
GuyW

I do have a solution, though a bit drastic so it's something of a last resort. I could cut the straight bit of tube mid way between the cover plate and the canister. Rotate the canister a bit more upright and then sleeve or weld it. Or even join it with a short bit of rubber hose if I can find something of the right diameter.
GuyW

So I have a front tappet cover canister breather from a 998 mini that doesn't fit. And Moss lists this part as 12A1212, which is the same number that they list for the equivalent 1098 Spridget part. 12A1212.
That suggests it is the exact same item but is it possible for two variants of the same part, with differences, to still have the same part number?
Does anyone have a copy of the correct parts list reference for this part?

The Moss item isnt expensive at just £22. I could just order one but dont want to end up with multiple copies of the same non fitting part!
GuyW

The original BMC parts book lists three canisters for the 1098 Sprite, 12G577,12G833 both of which appear to be have been replaced by 12A1212
Bob Beaumont

Re. images. All images contain meta data which describes the orientation of the image (amongst other things). If the application you used to invert the image doesn't have the ability to over-write the meta data it will always be wrong when displayed by an application that obeys the meta data.
I've used Paintshop 6 for years and years because when it saves the image it erases the meta data and any application that expects meta data but finds it missing has no option but to display the image in the orientation as read from the file, rather than manipulating it according to the meta data.


MG Moneypit

Some bolts on our cars originally had a beveled lead in to the screw. One example is the long screws that secure the gearbox mount to the chassis. Unfortunately, when buyers order new ones from suppliers they don't have the technical knowledge to understand the reason for this. Or (more likely) they are cheaper so let the customer spend fruitless hours getting the gearbox mount into the correct position for the threads to catch, or more likely, cross thread and have to buy some more.

Rob
MG Moneypit

Rob, thanks for that info about photo metadata. I didn't know that. Oddly though this is the first time ever that I have had a problem of inverted photos on the BBS. I often wondered why others reported the same issue, and had problems. I never had, until now. Something's changed, maybe a software update somewhere.

I have often added a bevelled end to a bolt where centring was awkward. It's so quick to do with a file or grinding wheel and can save hours of cursing! Only I never called it by the posh term of bevelled lead. To me it's just a pointy end! 🤣
GuyW

Bob, thanks for that confirmation
I think I will try ringing Moss when they are back at work tomorrow and see if their versions of 12A1212 differ between mini and Sprite.
GuyW

It seems 12A1212 was also fitted to later 1098 Minor!
Bob Beaumont

My suspicion is there are variants of the 12A1212 part. Mine doesn't have the two rings, which could be a distinguishing feature for the parts bin. The positioning of it is really tight, fitting between the carb heat shield, the exhaust manifold, the top radiator hose and the heater delivery hose. The only ones of those that have a potentially variable position is the water hoses. Shortening the straight top section to the water pump would move it a little and could work.
GuyW

Guy, I found the one from the 1098 Midget we had here. It is the proper one with no fit problems. A couple of photos.





Paul Walbran

Thanks Paul. Well established that mine, off a 998 mini doesnt fit. The canister leans forwards more, and leans in at the top. But the mini and the 1098 Sprite ones still carry the same part number, despite being different. 🤔
GuyW

I think the “3 section” canister indicates it’s an original design, as I don’t believe any of the repro ones have that, they’re just a plain finish.

At one time I had an image of original and new canisters together which showed the different angles between them. Again, just poor manufacture resulting in a bad outcome.
Philip Sellen

Philip, mine doesn't have the two grooves. So it could be a repro. one. But equally the absence of grooves could be to distinguish it from the Sprite version as the angles of the canister part are distinctly different, and which is why it doesnt fit my Sprite.
GuyW

I managed to find the image. A significant difference in the canister angles.


Philip Sellen

Yep, mines as the top one.
Its just that I suspect that the absence of the rings is to make it easier to distinguish, not because its a poor copy! Top one is for the 998 mini. Very similar but intentionally at a different angle.

The cover itself is also of the convex variety, with a folded over flanged edge to take the later rubber gasket rather than the cork ones.

What threw me was that Moss use the same part number for both! Its why I asked at the start if this was an error, or if different parts ever used the same number.
GuyW

Ringing Moss was inconclusive. I thought they might have clarified the issue of the 12A1212 part number being used for both Sprite 1098 and mini 998 when the parts themselves differ. And more relevant, I wanted to check before ordering that their 1098 version wasn't just a mini one wrongly assumed to fit. In the event, although they list both, with prices, they don't stock them.
GuyW

Making progress. I now have a canister type breather that is attached to the front tappet, AND fits the car.
Anyone know if it should have a stainless steel wire pan scrubber inside, like the 1275 ones?
GuyW

Yes, should do
Paul Walbran

Thanks Paul
GuyW

Ok, I now have a stainless steel wire pan scrubber. Given 'my friend's' recent fun day pouring contaminated fluids into the oil of his other car, this feels slightly risky, effectively stuffing metal wire wool into part of the engine that is also open to the lubrication system! What's to stop fragments detaching and working their way back into the tappet chest and down to the sump?

Actually, that applies just as much to the 1275 engines as well, and I've never even given it a thought before!
Engine paranoia with increasing age?
GuyW

The mesh in the factory assembled cannister is pretty well indestructable, and not easily removed. I think it's located by a steel wire clip too.

How come yours is missing? How are you going to put the new mesh in?
anamnesis

Canister is empty, which is why I asked.
But the tappet end of the canister is wide enough to push one in from there.
GuyW

Yes I know. Which is why I asked, how come?

And then hook it up vertically, once you get in in from the tappet cover end?

How about slicing the top off the cannister to add the mesh, and brazing it back on?
anamnesis

Anam, there wasn't one in it when I got the breather. Thats how it came to me. That's why I asked if there was supposed to be one and Paul said there should be.

To put one in, I would thread a cord through it, feed the end of the cord through the canister and out of the top. Push the mesh in from the tappet end which is about an inch diameter, and then pull on the cord to lift it up into position in the canister. Then remove the cord. No need to cut into the canister.
GuyW

A suggestion for once you get it in there, shake it vigorously so that any loose pieces of wool come out preventing any from potentially getting onto the engine.
Martin

Thanks Martin. I've just put the pan scrubber in - worked easily with the cord. I the blew the airline through it, washed it in petrol and then airline again. Nothing seemed to come out so either that hasn't worked, or nothing broke off in the first place!
It's drying now, for fitting tomorrow. It will be interesting in the end if it has reduced the scroll seal leakage at all!
GuyW

Guy, a believe it or not episode! Today we were sorting through a batch of stock we bought from a local company whose owner is winding down and retiring. And hey presto still in its original BMC box was a brand spanking new 1098 breather! All lines up with the grotty rusty one we have. The "pan scrubber" is all bright and shiny and looks exactly like that. I can just see the bottom of it at the top the connecting tube, and the top of it would be aligned with the upper groove in the body of the canister.

Now for the intriguing part. The part number on the box is indeed different from the 12A1212 Mini item, but at 12H1854 sounds like B series. However, I don't ever recall seeing that configuration on the B series, they had the oil separator built into the cover ... unless it was used in the 3 bearing version when the PCV was introduced. Not many of them around, only ran for 1964 model year.

Or maybe the transverse 1800.

But without measuring/trying it I can't see it clearing the exhaust manifold.
Paul Walbran

Plot thickens, Paul! Earlier Bob posted:
The original BMC parts book lists three canisters for the 1098 Sprite, 12G577,12G833 both of which appear to be have been replaced by 12A1212. So there's more random BMC numbers?

Quite apart from sorting my specific little task, I was posting a broader discussion about whether a single part number such as the 12A1212 one might be used for different variations. Now it almost seems that different numbers might be used for the same part!

Anyway I took the pragmatic approach with a slitting disc and welder, adding a slight adjustment to the tube section between the tappet cover end and the canister and it now fits perfectly, avoiding manifold, heater pipe, top hose and heat shield, all of which were within contact range of the 998 mini 12A1212 version I had.
GuyW

Worked it out, false alarm sorry. Austin 1800 breather. It is a 12H number which indicates B series. Not on any MGB I can remember, then the land crab occurred to me so I went looking. Google images are very helpful.
I had better recheck the measurements.
Paul Walbran

Moss quote the same part numbers for tappet chest cover gaskets for A-series and B-series, so they're obviously the same overall size.
Dave O'Neill 2

Bit of a saga, this has been, but all back together and to me at least, it looks like it was supposed to be!


GuyW

Is that a non-standard heat shield?

It looks very close to the rad bottom hose and you wouldn’t normally expect to have to cut out a section like that to give access for the canister.
Philip Sellen

Philip, it's an aftermarket SS heat shield from Ashley Hinton, I think it was. The carbs didn't come with one. Plenty of clearance from hoses but not for the canister, hence the reshaping cut out at the front. I might take a little more off there yet to give a bit of extra clearance.
GuyW

And an update on this breather system on my 1098 Frog.
The engine was prone to quite considerable rear scroll seal leakage with the passive draft suction tube that the engine originally had.

First I made a little 'nappy tank' cut from the top of a 1 gallon oil can and bolted under the engine rear back plate. This worked in as much as it did collect oil, but I continued to get oil drips from all the other bits of the car underside where it gets blown to with the car in use.

I then upgraded to a PCV system using manifold extraction, a PCV valve and a take off from the front tappet chest cover via an oil fume canister. That was the bit I was having difficulty identifying and sourcing. It ending with me doing some cutting and welding to modify a mini version to fit my car.

This now seems to be doing its job. After about 100 miles of use there are ZERO drips of oil on the test card that I put under the engine when its parked up on the drive, or in the garage overnight. Well pleased with myself!
GuyW

The downside to a leak free engine might be the need to rust proof the tunnel area. The late John Mead told me of a spridget owner he knew that proudly talked about his leak free engine and John said it was the only one he knew of with a rusty tunnel.
David Billington

This thread was discussed between 22/04/2023 and 25/05/2023

MG Midget and Sprite Technical index

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