Can someone explain how this PCV valve should work
Mine just seems to suck heaps even with the internal plunger all the way down
Mine originally had no spring and i was given a cut down SU spring to use from a well known Mini Mechanic locally
When the engine was out i thoroughly cleaned out the breather can on the tappet cover and fitted a new breather type oil filler cap

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1970 MK2 Cooper S

Here you go.http://www.mgaguru.com/mgtech/engine/cv103.htm

Modern PCV valves are much simpler. I now run a Toyota style PCV13, it works just as well. But my car is a bitsa, so no originality issues.

http://www.motospecs.com.au/assets/file ... itches.pdf
[edit] scroll down to p17 for pics.

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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.

Interesting read Doc.
So the normal Mini PCV relies on atmospheric pressure (through the small hole in the "top").
Do the Toyota ones work the same way?

No idea, but they work fine. So do they on 99% of more modern cars.

Edit
There's a cutaway view and explanation here
https://m.youtube.com/watch?v=UegCOOM3e_Q

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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.

Modern PCV valves don't need a vented cap.
The lower than atmospheric pressure in the crankcase sucks air in past the crankshaft oil seals.
With the engine running it minimises oil leaks past the seals as well.

Did the Cooper S really need a vented cap?
The cap was supposed to be changed every 12000 miles.
I've only ever bought one vented oil filler cap in nearly 50 years and it doesn't seem to have made any difference.

RonR

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68 build Mk1 Cooper S
72 Clubman GT project. Total restoration required

This PCV valve doesn't shut off completely when the valve is pushed all the way down
So i guess it is fardookered
Might have to invest into a new valve

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1970 MK2 Cooper S

I don't believe it should totally shut off. The 4 grooves in the body limit the airflow at high vacuum.
I have run 1275s with the Smiths valve for years, with and without a vented cap. Seemed to make no difference.
My 1412 had a sealed cap and the 1360 a vented one.
The test for it working is put your hand over the oil filler hole, you should feel vacuum.

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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.

The write up you posted said this
As the poppet approaches the valve seat it restricts air flow. The internal cavity of the valve body is then isolated from manifold vacuum and is exposed to the lighter vacuum level in the crankcase. If the poppet was to closed all the way it would stop air flow completely,

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1970 MK2 Cooper S

I will test my Smiths one for shutoff tomorrow.

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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.

With the valve pushed in, no it doesn't seal off. I can suck through it.
However it feels like there is a reed valve in there which sudden opens as you apply a little vacuum.
The valve still works fine I have had it on a friend's 1310 for the last week.

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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.