Hi everyone,

I realise this topic has been discussed numerous times, I have searched the forum but what I am reading doesn't seem to quite make sense so hoping to gain some clarity!
I have an 1100s 1275 engine. Has the breather coming off the flywheel area and one popping out the back next to the radiator. I have a rocker cover with a vent hole in the top. Running a weber carb with inlet manifold with two uneven sized holes currently blocked.
At present all of these are open to atmosphere. I also have plenty of oil coming out from pretty much everywhere so either it's just a mini thing or I have ventilation issues.
I have read that air is meant to suck through the rocker cover and out the breathers, but at present I can feel air pushing out of the rocker cover and the flywheel one. Not sure about radiator side one due to fan proximity.

Can anyone suggest which pipes to where and which ones need a pcv?

Thanks in advance

I had 1100s, 1275 with a webber and the only ventilation I had was from the tappet cover to the air filter and the car had no oil leaks at all. I would say that you have greater issues than just ventilation if you are leaking oil out everywhere . Time to do a compression test I'd say.

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"Investing my Super in a Cooper" &
"Re-living my Surfing Past in a Woody"

I put a PCV on both of my inlet manifold take-offs. My car has 2 rocker cover breathers only.
One is plumbed into the intake manifold through a PCV and the other goes through the charcoal canister first then through a PCV to the intake manifold. The PCV valves and hoses I got from the wreckers for $5.
Originally it had a 5 litre oil container as a catch can vented to atmosphere.

Standard, an 1100S just had the flywheel housing (actually, drop gear housing) breather, it was connected to a Smiths PCV valve and ran to the manifold. Air was admitted through the oil filler cap, which had a `filter' and a 4mm restrictor hole in it.
Comment:
If it is blowing air out the breathers now, you have a ring blowby problem. A PCV valve won't fix this (been there, done that).

re the Weber manifold- you can put the PCV valve into one side only. However this buggers up the idle mixture, which you then need to set richer on that side to compensate.
I used brass fittings to add a 3/8 bore balance pipe, with the PCV valve into one side, and the vacuum booser the other. The PCV valve I'm using is a Toyota style one, from the rocker cover. I have no flywheel housing or timing cover vents.
The other fittings you can see are the water heating, which I added to eliminate carb icing on the freeway.


Note the PCV valve is designed to pull a slight vacuum in the crankcase. If you do not restrict the air inlet, this won't happen, and it's more likely to pull oil thru the PCV valve from the fog existing down there. The breather can is not an oil separator. It's a flame trap.
Laingy found this out the hard way.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks for the responses.

So if I have a line from air filter to rocker cover (restricted), then have the two breathers connect to a pcv, then to catch tank, then to inlet manifold will that be a theoretically correct setup?

You shouldn't need a catch can. That's mainly for racing or bling points.
I would route the 2 main blow by areas ( Rocker cover and Rear breather ) into the inlet manifold via a PCV.
The other breather from the drop gear housing should have less oil so I would run into the aircleaner. There will also be an unrestricted path for air to go back into the engine if the intake manifold sucks to much at idle.

If it is an 1100S motor where is this `rear breather'?
If on the fuel pump hole, I would lose it. I made one for there once. The crank and rods throw oil straight up it over 4500rpm. Was fine, during running in.. rofl.
Mine is on the rocker cover because on long LH bends at high rpm, the primary gear threw oil up the `flywheel housing' breather. I have had no probs using the rocker cover, let's face it 90% of modern engines put their PCV valve there (or on an overhead cam box).

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

My 1100S has only one breather.
This is from the rocker cover. The hose just dangles down beside the flywheel housing.
Nothing ever comes out of it (well, no oil anyway). This is how my professional mini mechanic did it.

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Find a job you love and you will never have to go to work !

Haha that's a classic. Reminds me of the original 850 - a hose off the side cover, straight down the back!

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

It is the one off the timing cover like the one below:

Probably still cleaner than a VW TDI

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Find a job you love and you will never have to go to work !

Hi all , I've been reading this thread with interest I only have a breather on the flywheel housing, this is just vented to atmosphere through a filter cap on top. My question... Is there any advantage to having a pcv valve, other than for emission reduction? Richard.

A PCV valve (or the vac port on the side of a later SU) pulls a slight vacuum on the crankcase.
Benefits for road use:
Less engine smells in the cabin.
Less oil leaks through seals.
Less or no mayo in the rocker cover during short runs in winter.

For track work I used to clamp the hose on the PCV and run both breathers to a catch tank.

re the PO's timing cover breather, these were never used on the Morris 1100S; it's probably off a 1275LS.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I guess I probably should have said that in the first place... My car is a 1275ls.

Anyone out there in 1275ls land still have the original emissions setup? How was it setup? Did this model have all 3 breathers or have I acquired an additional one?

Btw reason I didn't mention was 1275ls - I thought they were the same engine... I guess essentially they are but with a few bits changed that I didn't realise...