I have a feeling CCV had different meanings depending on who you talked to, and maybe even within BMC. I have based my usage on codes published in various factory parts catalogues. The frame below is from the Mini parts microfiche AKM1145FK which references both PCV and CCV. If you Google "carburettor crankcase ventilation" (in quote marks) you'll find quite a few hits relating to BMC engines. Maybe other manufacturers used the term closed?

Edit: Googling "closed crankcase ventilation" certainly does bring up lots of hits for other vehicle manufacturers describing the same emission control setup.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

For those wanting a technical explanation of how CCV works this page is from the BMC Emission Control workshop manual supplement AKD4957B. The system uses the vacuum source on SU carbs referred to as 'constant depression', which is the area between the butterfly and the piston. You can see the (blocked off) tubes coming out of the carby bodies in glenndunn's picture at the start of this thread.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

My Clubman GT "project" has the AEG573 manifold but uses the Y piece pipework and no PCV as above.

RonR

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