Morris Minor Owners Club

Good afternoon everyone,
I've a 1275 Midget engine for my Morris. It has (or should have if it wasnt broken off) a breather/oil separator can on the timing chain cover. This would be connected by a hose to the inlet manifold to vent the block of any fumes. If I substitute a plain (without breather) Minor chain cover and use a Minor rocker box cover with a breather pipe on it, would it be an acceptable way to vent the crankcase fumes to the manifold? To me, the fumes are still vented but just by the Morris route rather than the Midget way. Any opinions are appreciated.
Thanks, Colin.

The 1275 needs a bit of extra breathing, so ideally you should use both! If you seal up the front, then you will get oil leaks fairly quickly.

the rocker cover vent is an outlet, and needs an inlet - this is done via a tube off the front tappet chest cover.
For the midget, there are no tappet chest covers so that is not a good option as you're missing an inlet - therefore the usual way is to slim down the timing chain cover breather so it clears the fan, and to use a vented oil filler cap as the inlet (they have a wire mesh strainer/filter). Or you can use the vented rocker cover as an inlet with a little filter on it, but that looks a bit more obvious / boy racerish.

The reason to have an inlet an outlet is to get a flow of fresh air through the block so as to help remove condensation. Condensation can't be avoided and unless it is removed you'll get sludge. With a high mileage engine you also need plenty of breathing to help vent any blow-past otherwise the crankcase pressure will cause leaks.

If you can, get hold of a copy of David Vizard's 'Tuning BL's A-series engine' it explains about the breathing needs of engines, as there are a lot of myths doing the rounds.....

[quote="doobry"]the rocker cover vent is an outlet, and needs an inlet - this is done via a tube off the front tappet chest cover.

Really? I thought the filler cap was the inlet. My recon engine came with a bent pipe on the tappet cover and a pipe on the rocker cover, whereas the original engine had a cylindrical (gauze internal, I assume) oil separator on the tappet cover and no pipe on the rocker cover.
I've connected the tappet cover pipe to the carb and blocked off the rocker cover pipe. Is this OK? (as I'm using a "breathing" filler cap)
It's certainly not using any oil any more (the old one did!).

Stig the engine in question is from a 1275cc Midget and the breather comes from the timing cover there is not a pipe on the tappet covers on the Midget engine, which type are you talking about 1098cc ?

The idea behind the breathers is to stop the crankcase pressure being higher than the pressure outside the engine (due to combustion pressure leakage past the rings) and so they prevent the pressurisation of the seals and them blowing out!

If you attached a filter that was open to atmosphere on all your breathers then your engine would be fine. Some combustion fumes get inside the crankcase and in the case of the A-series (and a lot of later engines actually) they are 'sucked' out by the connection into the carb and are burnt again in the combustion process, which is why it is important to have an 'inlet' for the air if you are sucking it out via the carb/inlet manifold.

In fact this system would run at slightly lower internal pressure than without, and Vizard has done experiments and has shown that engine performance is much better with a vacuum inside. But for a normal A-series engine the vacuum is negligible anyway.........

STIG.....assuming that you have the 1098 engine then it is quite
simple...If your car vents into the AIR FILTER then you should have
an inlet pipe on the tappet chest cover and a SOLID (no filter)oil
filler cap. If your car vents into the CARB itself you should have
an oil filler cap which has a wire mesh filter in it.

Sorry guys, wasn't very specific there was I? Yes, it's a 1098, but with a Metro carb hence the venting into the carb. Which conveniently makes it roughly the same as my Sprite (1275) which has the oil separator on the timing chain cover which also vents into the carb(s).
Though come to think of it, the original Minor engine (1098) vented from an oil separator on the tappet cover into the air filter. Hmm. It did need the oil topping up every 300-400 miles though, but then it had done over 190,000 by the time I replaced it so I could hardly complain!

the original Minor engine (1098) vented from an oil separator on the tappet cover into the air filter

Was that fitted on the moggies? I've seen them but never really knew if they were original fit or an Austin version of the engine, as most of the 1098's I've had had an inlet/vent on the tappet chest covers, not an outlet to the carb.

I thing it was on the later produced 1098cc engines that the outlet to the carb was used, probably to do with overseas emmisions laws, and the Austin engine was just the same engine with a different badge.

DOOBRY... according to my info the 1098 Minor engine was NEVER
fitted with an outlet from the timing chain cover. The later 1098s
had an outlet from the FRONT tappet chest cover which fed
via a spring loaded valve assembly on the inlet manifold into the
carb. The spring loaded valve assembly caused more problems
than it solved and was quickly eliminated so that the FRONT tappet
cover had a simple oil-trap fitted to it from which the pipe
fed straight into the carb. Both of these types should have an oil
filler cap with an inbuilt filter. All other types should have a solid
oil filler cap.

well, alot of reading there. Thanks for all your replies. Looks like it'll be best for me to get a new timing cover with the breather on it. I'd also forgotten about the rocker cap having a breather in it too. Now its all explained, it all makes sense. Thanks again, Colin.

Willie,
Thanks - that explains the ones I've seen with tappet chest breathers. Some were later cars but others were early cars with 1098 engines added so I was never really sure if that was a proper moggy thing or just came with the donor engine.
I'd presumed that the early 1098 rocker-cover breather to the air filter was the correct one for all, not just for the early 1098's. You live and learn

Hello all,
I had the same problem as Colin when I fitted a Marina engine to my wife's traveller. My solution was to cut and blank off the front timing cover breather system. I retained the 1098 rocker cover breather into the carburettor air cleaner and made up a crankcase breather pipe as per the 1098 engine but bolted it to the mechanical fuel pump aperture. This system seems to have worked quite satisfactorily.

Alec

My solution was to cut and blank off the front timing cover breather system.

The easiest thing is to change the breather or flame trap from a cylinder shape into a `D` shape then there is sufficient clearance.
I have also seen it replumbed to a different location so that all thats left on the timing cover is the width ot the pipework.

Kevin wrote:The easiest thing is to change the breather or flame trap from a cylinder shape into a `D` shape then there is sufficient clearance.

Like this:

http://potteries.mmoc.org.uk/Members_Ca ... 412_03.jpg

Nice one Cam, the picture says it all.

Hello Kevin,
sorry but that looks rather messy to me, I prefer my soultion which copies the original valve chest shape breather.

Alec

Hi Willie, forgive my ignorance, but could you explain why the right filler caps need to be fitted as per your quote below. Thanks.
Jono

[If your car vents into the AIR FILTER then you should have
an inlet pipe on the tappet chest cover and a SOLID (no filter)oil
filler cap. If your car vents into the CARB itself you should have
an oil filler cap which has a wire mesh filter in it.][/quote]