1275 pre A+ engine Breather arrangements

[moggiegeek]

I have 1275 as above about to be installed. Not sure about crankcase breathing arrangements.
I have timing case breather and could fit a rocker cover either with or without breather tube. I imagine the rocker breather and timing case breathers would join and go to HIF38 carb. Or should I just have the timing case breather?
Which is the right arrangement?
What sort of rocker cover cap is needed?
Many thanks.

[philthehill]

Breather/oil separator on the timing chain cover connected to carb.
Rocker cover without breather pipe.
The type of oil filler cap in the link below: -
https://www.morrisminorspares.com/engin ... 03-p830482

[jagnut66]

Another option, if you want a Chrome finish that's vented, I fit these:
https://www.ebay.co.uk/itm/255635339583 ... R66eqtDpYA
Best wishes,
Mike.

[moggiegeek]

Thank you, it deserves a bit of chrome!!

[Chipper]

Does anyone know how to arrange the crankcase breathing for a 1275cc MG Midget engine (12CE) fitted with a Weber 40DCOE carb?

I recently fitted one to mine (in place of a SU HIF44), left the crankcase breather pipe from the oil trap canister on the front of the engine open to atmosphere and took it for a brief 20-mile run and noticed a load of engine oil gushing out of the bottom of the gearbox bellhousing; it had blown most of the engine oil out of the rear crank scroll seal, at a guess!

[philthehill]

If the front oil Seperator/breather is clear there should be no reason that the crankcase fills with blow past pressure so pushing oil out of the back of the crankcase/crankcase scroll.
Firstly, remove and make sure that the oil Seperator/breather is clear. If it is not that could be the cause of the problem.
I have run 45DCOE carbs on my Minor for some considerable time and have never had crankcase pressure blow oil out of the back of the crankcase/crankshaft scroll. The oil Seperator/breather on my engine is vented through a pipe to a catch tank and I have never yet had to empty the catch tank which is fitted with a sight glass.
You could fit a PCV valve to the inlet manifold and connect the oil Seperator/breather vent pipe to the PCV valve.
Below: - This was the breather arrangement when fitted with a single 45DCOE carb.

WDF engine 8.jpg (71.51 KiB) Viewed 1272 times

Pipe from the oil Seperator/breather to a ' T ' piece serving the rocker cover vent and from there to the catch tank. From the catch tank a pipe to vent adjacent to the air cleaner.

[Chipper]

Thanks, Phil. Just how 'adjacent' is that pipe to the air cleaner, and how do you find it runs on a 45 DCOE (I presume you have a 1275, and what appears to be no vacuum connection to the distributor)?

My 40 DCOE is currently fitted with trumpets, and a 'RAM AIR' filter sock; I was considering the fitment of the type of cleaner you have - may I ask where you acquired yours from?

I didn't previously have any such issues with the previous HIF 44 (which had the crankcase ventilation stub), so I assume the oil is being forced out as a result of the lack of crankcase breathing/vacuum as a result of fitting a Weber...

[philthehill]

The end of the vent pipe is up against the perforated air cleaner case
It ran very well with the 45DCOE 13.
The engine was 1400cc.
No advance to the distributer which is based on the Cooper 'S' distributer which does not have a vacuum advance ex-factory. Ignition advance is controlled by the balance weights/springs and limited by the advance limit stop. The distributor advance curve was matched to the camshaft.
The air cleaner came with the 45DCOE carb. I do not know of a source for a similar air cleaner. There were short trumpets fitted inside the air cleaner.
If your oil Seperator/breather is blocked and you do not have a vented oil filler cap you will not have any crankcase breathing/ventilation which is an absolute must.
Below is the oil Seperator/breather (ex 1275cc Marina) fitted to my Minor 1380cc engine.

WDF engine 6.JPG (1005.87 KiB) Viewed 1249 times

The oil Seperator/breather can be cleaned out from the inside of the cover and a stainless-steel pan scrub fitted.

[Chipper]

Well, I tried re-routing the crankcase breather hose from the canister on the front of the engine directly into a tap on the Weber 40DCOE inlet manifold, took it for a wee spin yesterday, and rather than blowing engine oil out of the rear scroll seal, it instead sucked it into the engine and I was followed by a huge cloud of smoke out of the exhaust, resembling Del-Boys Reliant Regal, which got me some aghast looks from bystanders!

I've now reverted back to the SU HIF44.

[philthehill]

I am not surprised that you are getting oil sucked into the engine if you have a direct feed from the crankcase breather/oil separator to the inlet manifold. There must be a PCV valve fitted between the breather/oil separator and the inlet manifold.

[Chipper]

Ah well, I prefer the SU for winter use anyway since it has a choke control (my 40 DCOE had this blanked off).

I may have another go with it next year when it gets warmer...

Thanks for the advice.