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MG Midget and Sprite Technical - Engine breathers?

Looking to fit a couple of breathers into the sump.

Had a quick look tonight to determine where they might fit and realised there is very little room!

With a turbo on forget the passenger side of the engine!

Yet the drivers side we have the starter motor, engine mount and oil filter so has anyone (Rob?) found a good place to fit on the sump?
Robert (Bob) Midget Turbo

I fitted a 1" breather into the rocker cover and another with oil separater to the fuel pump boss, any oil drained back to the sump via a 1" sump connection below the fuel pump boss. The sump connection having an anti-surge flap to stop oil flowing up the sump connection during cornering. I'm sure you'll find space somewhere, be inventive.
David Billington

Hi Bob
Tricky one this, not as much room as you think, my sump breather is fitted just left of the spin on filter, if you whent any further to the left I think it could cause problems getting the starter motor off.
As you say drivers side is a no no, so if you want two breathers best of luck finding somewhere for the second to go !
Picture shows a breather to the dipstick (blue) and 1/2" breather to the sump (black)+ I have one to the rear of the timing cover and two on the rocker cover.
Best of British luck, you will need it to stop that leak !


Rob Newt

Extra breathers can help reduce oil being pushed past the scroll only if they vent excess pressure from the crankcase; this only happens if the current breathers are inadequate (ie. they don't have the capacity to flow the excess gasses) and the new ones more effective. Just where in the block / under the valve cover is the excess pressure you want to relieve?

Vizard recommends using exhaust-derived vacuum on high-performance engines, since it's vacuum that's really needed to help the scroll work. And to maintain this vacuum in the block / rocker cover, you need fewer rather than more breathers, otherwise the breathers let in fresh air and don't allow the vacuum to be maintained.

IIRC someone has already mentioned the exhaust/vac system in recent post.

I understand you can't have a vacuum in competition engines, since they must have a breather (vent) pipe into a container that prevents a vacuum forming, assuming of course the original breather (vac) pipes to the carb/manifold were left in place or you have exhuast-derived vac. This is why many competition engines use a proper seal on the back of the crank.

[When I added a vent pipe to BRB for hillclimb, the sroll then leaked when engine was hot, so I plugged the vent pipe and the leak stopped; vac came from HS6 ported carb.]

You will recall the original engine 'breather' is the vacuum pipe from the carb / inlet manifold. The only other 'breathers' are the rocker-cover cap, designed to let a miminal amount of air through, and the scroll which breathes in to keep the oil on the other side of the scroll.

A
Anthony Cutler

Thanks for the comment Ant

But this is where I am


I started with a manifold vacuum device and breather from the front timing cover and a small one in the rocker cover.. Result oil peeed out

I then fitted a rear seal kit.

Oil peeed out

When inspected rear oil seal was damaged due to contact with flywheel. I then modified the flywheel to clear the seal replaced it and fitted a 22mm breather to the dissy outlet (I have and ECU fitted)

Oil peeed out

I Then fitted a evacusump into my exhaust system

Result oil pees out?

Maybe I need to take stock? and start a fresh!
Bob Turbo Midget England

Ok; if you have Evacusump, you should block all the other breathers to allow the evacusump system to suck air out of crankcase and create a vac.

Other than that... you seem to have tried everything... you need to catch the oil in a tray attached to the bellhousing and pump it back into the engine!

A
Anthony Cutler

Bob,can't remember what ignition system you have,but getting rid of the dizzy gives a very large extra crankcase breather...........
steve cowling

Hi Steve yep I have a front pulley trigger and so am already have a 22mm breather on the dissy outlet.

I just don't quite get how blocking up the breathers helps to stop leaks? but it might be what I will have to try.
Robert (Bob) Midget Turbo

>>I just don't quite get how blocking up the breathers helps to stop leaks?

If your evacusump system is working, it should be sucking air down into the exhaust. If you connected the tube to an empty air-tight box, they'd be a slight vacuum in the box. Make holes in the box, and the vacuum goes away as air leaks in through the holes.

In your case, you want the air leaking in only past the scroll and so keep the oil in.

BTW - assuming the evacusump system works, it's likely to be better at high exhaust gas flow, and less effective at idle.

A
Anthony Cutler

I have been looking at my breathers because there was lots of oil dripping from the car. I found that my oil catch tomato sauce bottle (I really should get round to buying a proper tank) had 1.5 inches of water and oil emulsion in which covered the end of the breather pipe! Not that good for reducing the pressure in the sump. I have sorted that now but was wondering where I can get details of the evacusump systems you all seem to have and which rear seal systems work best?

Dave
D Brown

Bob,
i've ditched the evacusump after much testing due to pulsing & the one way valve fluttering which allowed exhaust gas into the sump.
At present dizzy breather using one of the evacusump oil catchers, rocker cover 3/4 breather, timing cover breather, 22mm sump breather on front NS using the other oil catcher & catch tank drain on NS rear below oil line.
No pictures to hand i'm afraid as i'm in Norway today.
Brad
Brad 1380

Point taken Ant but what happens if the "manufacture" of pressure in the sump/engine is actually more than the evacuation system can pull out? then inevitably the system will fail, wont it?

If you look at it in the following manner you will come to a different conclusion.

To get rid of pressure build up you can put pipes leading to atmosphere so that any pressure above ambient ought to be realesed through the breathers. On top of this if you have a suction system (manifold/evacusump)then that ought to compliment the breathers. What do you think?

Hi Dave I have tried the rear seal (they are all the same irrespective who you use as a supplier) and the first one failed because my flywheel was interfering with the seal. I machined my flywheel and hopefully the seal should now be in one piece I will let you know if that is the case in a couple of weeks time when I inspect it. Regarding the rear seal mine has not solved the oil leak problem. Evacusump is straight forward, weld a small pipe into the exhast flow and fluid dynamics should cause a low pressure (suction) area in the pipe. This can then be connected to your engine breather. Mine did not work as well as predicted and did not cure the problem although I am running more that 20 psi of boost.

Brad

I have almost the same as that except for the 22mm sump. How is your oil leak?
Bob Turbo Midget England

Ive read all the threads there are on engine breathing and the different issues people have and I just dont get it. I understand it but I dont get it. My experience is that the standard system works well as long as you dont start adding other stuff to it, like riddleing the block with gapeing holes that make it impossible to achieve any sort of negative pressure around the scroll.
What I do know is that with the standard set up my car drops the odd bit of oil. After some maintenance I forgot to reconnect the breather valve back onto the inlet manifold, meaning the tube from the canister, with the valve dangling on the end, was effectively blocked. This left 2 places for the engine to vent, out through the pin hole in the rocker cap, or out through the scroll. It did both, leaving mist all over the underside of the bonett and a lake of oil on the garage floor - I thought the engine had a hole in it at first, however after reconnecting the valve back onto the manifold I was back to just the odd drip.
Prior to me re-establishing the current standard system (onto a weber inlet manifold)The PO had removed the breather valve,drilled the rocker cap so it looked like a tea strainer, plugged the inlet manifold, vented the cannister to a catch can, welded a take off onto the sump and piped this through the transmission to the rear axle. The pipe had then rubbed on the prop shaft and worn a hole in it which resulted in fumes coming up through the gear lever opening, an awfull lot of oil on the underside of the car and an egine bay soaked in a mist of oil. Parking the car in the garage after a run was a no no because the stink of oil would fill the whole house. What was he thinking?

I know most of you guys know far more about this than I do, and that most of the time you are talking about different, or modified engines, but I thought I'd just chip in anyway.
S G Macfarlane

Thanks Bob,
After reading S G Macfarlanes comments I think I should be going back to the standard setup for a while. I was getting plumes of smoke when pulling away and oily carbs with the standard breather setup hence the catch 'tank'. I am now getting an oily garage floor.
I only have the atmosphere to provide my boost.
Dave
D Brown

>>Point taken Ant but what happens if the "manufacture" of pressure in the sump/engine is actually more than the evacuation system can pull out? then inevitably the system will fail, wont it?

>>If you look at it in the following manner you will come to a different conclusion.

>>To get rid of pressure build up you can put pipes leading to atmosphere so that any pressure above ambient ought to be realesed through the breathers. On top of this if you have a suction system (manifold/evacusump)then that ought to compliment the breathers. What do you think?

Hi Bob

IMO extra breathing holes undo any potential good from the evacusump. And if you're producing more crankcase gas than the evacusump can flow, then there's no point having it (evacusump). The only fix then is a rear seal (and breathing holes).

But remember, the amount of air pulled into the evacusump will depend on the rate of flow of the exhaust, so the more work the engine is doing, the better the potential vacuum.

- assuming of course: the evacusump pipe is installed correctly (pointing in direction of flow?)
- the engine doesn't create excessive crankcase gas at full chat
- the exhaust doesn't have excess pressure in it.

A
Anthony Cutler

maybe helpfull

arnold


a.o. arnold

Ant

I have an evacusump pipe in my exhaust with the open end facing the rear of the car, this has a non return valve between it and the engine with flow allowed towards the exhaust.

I also have a second system from the intake manifold again with a non reurn valve. I believe with the inlet manifold sucking at low throttle openings and the exhaust sucking a high exhaust flow rats I ought to be well covered.
Robert (Bob) Midget Turbo

Bob,
i modified my evacusump as per your internal tube, it worked well at idle & high revs however it was mid range that the one way valve fluttered & i could feel this with my finger on the breather pipe & my exhaust is pretty open too, so i don't think the system is suitable for a road car.
Still getting a few drips from the timing cover, but i have an ali belt drive, so the end plate cover doesn't seal against the main ali body & any oil will drip out, a small return hose from the bottom of the body to sump will be next.
If your going to put breathers in the sump you really need an Oxy set to braze them in, a plumbers blow torch won't get enough heat into the sump.
Brad 1380

OK just to update

I now have the engine out and the rear seal is in good condition (Now I have machined 3mm of the lip of the flywheel that made contact with the original seal and destroyed it. So that is good. In fairness I think the breathing and evacuation I already has seems to have been doing a pretty good job as the engine appears relatively clean. Perhaps the oil underneath in the garage was looking worse than it was? perhaps? however now it is out I am going to install a further 22mm breather.

Taking off ancilliaries I was able to see if there was actually somewhere to fit a breather of that size. On the driverside I could not find any suitable location anywhere it might have fitted would then have placed it directly below a sump screw and would then have inhibited the fixing of the sump!

The most/only suitable place I could find was on the passenger side on the angled part of the sump between the front and the side. Because it is angled the tube had to be cut at and angle and brazed into position to allow it to come out square to the engine. This places the breather between the first and second sump bolts on the passenger side and just behind the engine mounting.

I will not get the engine built up again until Monday as I am not picking up the sump gasket set until Sunday. I am pleased to say that I had used the black rubbery seals last time and they looked perfect when I took the sump off.

David With a Turbo fitted the xisting fuel pump boss is not available and would interfere with the turbo.
Robert (Bob) Midget Turbo

You might be interested in this...
I have been messing about with my breather set up and have gone from having a breather from the rear of the timing cover into rocker cover and vented out the other side via a small filter, I also had a breather on the dipstick and one on the sump, both vented to air via a filter
So I now have taken the one from the rear of the timing cover and put it into a catch tank and the one from the rocker cover also into the catch tank, the other two I have put into a seperate catch tank.
I have now reduced the loss of oil to a small drip even when giving it the full 173bhp !
(Has to be something to do with back pressure shurely)
Could someone please explain to me why this is?
Rob Newt

Sounds good mate.

I have now had my engine in and out 4 times in an attempt to solve massive oil leaks.

This last time I decided to redo the rear seal. The instructions from Peter May suggest we sould not use gaskets or sealer. I have come to the opinion that oil was building up behind the seal and then spewing out of the alloy pieces. I have now reassembled everything using blue hylomar on each part.

Just finished putting it together and all seems a lot better but during my test run car broke down!!!!!!! My wife rescued me with her MGF and tow rope so I now need to sort that!!!!!!!!!!
I think my programmable ignition has failed!

I already have 3 large breathers into a catch tank!
Robert (Bob) Midget Turbo

Rob, sounds like you have simply put the timing cover filter to air, thus giving the system an extra breather. Also, maybe your filters were blocked with oil thus in effect choking the breathing?

I have a couple of catch tanks to use, will put 2 small filters on each one making sure the bore of the filter hose is larger than the incoming breather pipe. Will report back when the car is running properly.

I have a question tho: what are people using for breather pipe? I have bought some silcon hose but it is pretty thick walled stuff, looks a bit dominant in the engine bay.

Bob, another question: have you done a wet & dry compression test? I am curious to know the difference in any in the readings.

Tarq
Tarquin

Bob, sounds like you need a compressor pump on the engine to make some vacuum! Prop can probably help you with that project.
Tarquin

Bob
You have had very different instructions than me!
Though i have not fitted it (yet?) i even got a tube hylomar with the kit (used that in my last engine build)
Onno Könemann

Hi Tarq. Yes I too use silicon hose and like you find it difficult to bend and rather imposing let alone expensive. However it can look tidy I think.

I will do a compression test before long to see the results but just for info I have measured the pressure when running and found it to be about .5mbar which I don't think is a lot. Plus the fact that it does not leak out of the front seal.

Onno funnily enough I had used sealer on the bottom half of the housing but not on the top section. I did get the feeling that he oil had leaked from around the top. Whilst I did not use gaskets I have now used sealer on all surfaces.
Robert (Bob) Midget Turbo

What is the history of the engine - pistons and rings in particular?
Tarquin

Bob - any news?
Tarquin

Yep

Bit of news Tarq

The last time the engine was out I gobbed the whole rear seal kit with HI LO MAR :)

I think now that I have seriously stemmed the flow of oil although still getting some when on "full Chat"

I seem to be having issues that I shouldn't and turned out that the ignition problem was actually the carb flooding. In the meantime I had altered the setting of my pickup that then was causing problems after I had sorted the flooding. That is all now sorted and been for a 100 mile blast today, man does that thing fly, faster than my F. :)

Anyway I will measure the Compression next week simply for peace of mind.

As it is running at the moment I will be entering the midget50 autosolo.

Pleased I will be able to enter otherwise I would have been feeling guilty at insisting they should change the date to the Saturday :)
Robert (Bob) Midget Turbo

Good news. I would like to hear the compression figs esp after comments on Bruce Roberts thread.
Tarquin

This thread was discussed between 05/04/2011 and 21/05/2011

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