A Motor breathing/ leaking as a result

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niftyrodman
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A Motor breathing/ leaking as a result

Postby niftyrodman » Mon May 04, 2020 7:31 am

I being one of the rear main seal addition mob, ,fitted long ago now wonder how by fitting that seal interferes with the action of the scroll. As well, I wondered if adding a breather to the fuel pump blank plate, would alleviate crank case pressure, better than the existing side plate breather, if I drilled the inlet manifold centre and fed it in there. The breather pressure at the rocker cover is fed into the air cleaner, but somehow I don't think the vacuum there is sufficient. Another question is: Can you buy a speedy sleeve to fit the rear of the crank.

philthehill
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Re: A Motor breathing/ leaking as a result

Postby philthehill » Mon May 04, 2020 9:51 am

I for one would not fit a crankshaft seal unless it was a properly engineered fitment as can be supplied by MED. See video link:-
https://www.youtube.com/watch?v=9sxy1pU ... _cNOfEoDay
The seal (if fitted to rub on the flywheel mount boss) will not interfere with the scroll but what you will not have is any suck (crank case depression) from the bell housing into the crankcase.
The suck as well as the scroll helps to return oil to the crankcase.
The breather on the fuel pump aperture is good and it is what I have and can recommend. As regards connecting to the manifold I do not know how well overall that will work. The usual place to connect to the inlet tract is via the carb body breather inlet.

As regards a speedy sleeve - what part of the crankshaft do you want to sleeve?
There is no way you can fit a speedy sleeve to the scroll or where the rear main cap and top half of the removable scroll cap fits as the shape of the crankshaft will not allow it.


niftyrodman
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Re: A Motor breathing/ leaking as a result

Postby niftyrodman » Mon May 04, 2020 10:49 am

Thanks for your reply, we think alike. The area I was wanting to improve was the seal bearing area at the crank end. I would have liked it to have been a better surface for the seal lip. I am really interested in your "suck' from the bell housing, drawing the oil back. Can you explain how that works. Thanks.

philthehill
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Re: A Motor breathing/ leaking as a result

Postby philthehill » Mon May 04, 2020 11:47 am

The crank case should be under negative pressure (depression) caused by the suck from the carb, the inlet manifold via PCV valve or the extraction of fumes by the breather pipe which goes down the side the N/S of the engine.
As the negative pressure in the crankcase is lower than that of the bell housing oil will be naturally be sucked/pushed towards the crankcase. What happens most of the time is that the crankcase pressure builds up and wear in the main bearings/scroll pushes the oil towards the bell housing. BL recognised this when they built the 1275cc Maestro engine and modified the rear of the crankshaft to suit a lip seal; plus they included a seal carrier housing to hold the lip seal. The conversion was very successful. Southam Mini Centre used to supply a conversion kit that allowed the 1275cc transverse Maestro engine to be fitted to vehicles with a in-line engine. Sadly the supply of these kits has ceased.
Below is the Maestro seal carrier housing which had to be modified to suit the in line engine.
Maestro rear engine seal plate.jpg
Maestro rear engine seal plate.jpg (419.62 KiB) Viewed 560 times


oliver90owner
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Re: A Motor breathing/ leaking as a result

Postby oliver90owner » Mon May 04, 2020 3:24 pm

The scroll seals worked (almost) perfectly well, long before crank case ventilation was converted to be negative pressure devices with closed crank cases. 0nly when the pressure became particularly positive, and the engine was well worn, did problems arise.

Edited to move a comma!19:18h
Last edited by oliver90owner on Mon May 04, 2020 7:18 pm, edited 1 time in total.

philthehill
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Re: A Motor breathing/ leaking as a result

Postby philthehill » Mon May 04, 2020 3:59 pm

It was not new or worn scrolls that caused the emission problems but the emission controls especially those imposed by the USA that required the piston bypass fumes to be consumed by the engine. The emission controls required for the USA market eventually robbed the engine of a considerable amount of power. Hop forward a couple of years and those emission controls/requirements imposed themselves on the UK market and here we are with all sorts of emission controls on modern engines.
Long live the crankshaft scroll.

Phil


niftyrodman
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Re: A Motor breathing/ leaking as a result

Postby niftyrodman » Tue May 05, 2020 8:59 am

Thanks Phil for your informative post. Y'now the breather pipe down the side of the motor that is designed to create a vacuum as you travel, and create that negative pressure you mention, primitive as it is, one has to accept as restorers, and that is what it is. I noticed on this forum a pic of a breather inserted into the centre of the inlet manifold, at the top, and I want to get an opinion as to how that would work, should I put a fitting in the f/pump blank, filter it in some way, or catch can it, and connect that to the top centre of the inlet manifold. On the pic it had some sort of diaphragm gizmo that may have been a vacuum restrictor. I thought it was interesting, The thing is, the rocker breather wants to blow more than the carb wants, at the pan cake air filter. Hot air from the crank wants to rise, that is understandable, but there has to be a way.

philthehill
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Re: A Motor breathing/ leaking as a result

Postby philthehill » Tue May 05, 2020 10:14 am

The usual way of getting the engine to consume the fumes is via the PCV valve which is fitted into the top of the manifold and which has a diaphragm inside it which opens and closed the PCV valve dependent upon the depression in the manifold.

You can put a breather catch can on the fuel pump aperture and feed from the catch can to either the PCV valve or carb.
The catch can will catch the oil being breathed and allow it to drain back to the sump.

Pancake air filter are not really designed to catch oil fumes - most do not have the facility to attach a pipe.

The best way is via the catch can to the PCV valve or carb.

This is what the inside of a PCV valve looks like:-
PCV valve 1.JPG
PCV valve 1.JPG (1.38 MiB) Viewed 459 times
PCV valve 2.JPG
PCV valve 2.JPG (1.32 MiB) Viewed 459 times
The above valve is the early type with valve plunger attached to the diaphragm. Later types have the valve plunger as a separate item.

If you do purchase a PCV valve make sure that it is the later type as the early plunger/diaphragm is no longer available.


Declan_Burns
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Re: A Motor breathing/ leaking as a result

Postby Declan_Burns » Tue May 05, 2020 10:36 am

MGB, Sprite/Midget, Mini Cooper S, TR4A
Part no. : 13H5191
Diaphragm 27H7758
Regards
Declan


Regards
Declan

philthehill
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Re: A Motor breathing/ leaking as a result

Postby philthehill » Tue May 05, 2020 11:28 am

https://www.moss-europe.co.uk/valve-ass ... soc=419722

The valve is not cheap but worth the purchase price.

There are after market valves available on 'e' bay and/or component parts available.

If you obtain an early PCV valve the later plunger/diaphragm will not be suitable as the early PCV valve casing does not have the plunger guides which the later valve has and which are required as the plunger is separate to the diaphragm.
With the early valve the plunger is attached to the diaphragm. If not attached to the diaphragm it cannot centre on the PCV valve passage to the manifold


newagetraveller
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Re: A Motor breathing/ leaking as a result

Postby newagetraveller » Tue May 05, 2020 7:16 pm

Is the existing breather pipe blocked?

niftyrodman
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Re: A Motor breathing/ leaking as a result

Postby niftyrodman » Wed May 06, 2020 10:03 am

I see. I see, the PCV. One could describe it as a one way valve, that restricts the vacuum. only allowing enough for a positive flow from the engine innards. I shall get one and drill right in the centre of the inlet manifold, then decide where best to draw from. You are right about the price Phil, but there you go. As an aside, one thing I found helpful holding the crank pulley was a chain wrench, as I have had two tries to stop a timing cover drip, despite a stiffener, "gold plated" hockey stick on the bottom. last go was using Ultra black silicone, following all the semi curing instructions. Im now down to one drip, a real nuisance. Modern oil is so skinny, almost as sneaky as Glycol. Gaskets you get are rubbish, if I have another go I will make my own gasket and use a hard setting Permatex No4. The 2 bottom bolts need to be drilled out to the next size and tapped, then use socket headed bolts, as with the existing, smaller bolts it is impossible to tighten them as firm as they need to be without danger of stripping that shallow threaded plate.So, gentlemen, I thank you both for the links.

philthehill
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Re: A Motor breathing/ leaking as a result

Postby philthehill » Wed May 06, 2020 12:03 pm

There should be no need to put up with a leak from the timing chain cover gasket.
Use a good quality gasket http://www.minispares.com/product/Class ... o%20search lightly smeared with grease. If you have to use goo there is something wrong with the parts you are using.
I have never had to revert to goo to seal a gasket on a 'A' Series. Different on a modern where you do not have gaskets only goo.
The 1/4" UNF bolts holding the timing chain cover are more than adequate to hold the cover in place. I have changed the 1/4" UNF bolts to 1/4" UNF cap headed screws on my 'A' Series engines as I prefer them to ordinary bolts.
The hockey stick is an sensible addition to strengthen the bottom of the timing cover and was added by BMC/BL to help hold the cover hard against the gasket/front engine plate.
The 1/4" UNF bolts holding the timing cover in place only need to be nipped up. Over tightening the bolts can not only strip the threads in the front engine plate but also distort the timing chain cover allowing the oil to slip past the gasket.
The timing cover must be centralised around the crankshaft pulley - if not the seal can leak and wear out quickly.
100_1232.JPG
100_1232.JPG (1.49 MiB) Viewed 337 times
No leaks from the above timing chain cover using the same gasket material as the minispares link with the gasket lightly greased and secured with cap headed screws.

Phil


paul 300358
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Re: A Motor breathing/ leaking as a result

Postby paul 300358 » Wed May 06, 2020 7:47 pm

It's worth noting that you don't need a PCV if you have fitted a hif carb. you just connect the oil separator to the connection on the carburettor. The correct rubber pipe is available from all the mini on line part suppliers.


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