Hi All, not sure if this has been covered before, some stuff pops up in a search but not exactly what Im looking for.
I have the aftermarket alloy twin inlet manifold for HS4, it has a drilling in the top for either the PCV valve,(or brake servo vacuum fitting), and a flat undrilled section next to it.
Im not sure if the PCV and brake servo fittings are different (although I suspect they are), I have one fitting but not sure which one it is.
Presumably I will need to drill and tap the flat blanked off section on top of the manifold to accept the brake servo fitting?
So i guess my questions are:
are the two fittings different?
what are the differences? (dia?)
are the threads different?
are they available?
Cheers,

Do your HS4 carbs have ports for the CCV breathers? That might be a better option than trying to use a PCV

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Cheers ‘Timmy’, but no.. I have the 1/2” nipple are lead to believe the brake servo nipple is 3/8”


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What are you trying to connect?

If you are trying to connect both you can simply use a T piece. If you carb has the CCV port it is better to use that for the breather and remove the PCV.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

I can't say for your HS4 manifold, but on my Cooper S HS2 AEG572 manifold both the PCV and servo holes are 5/8 UNF - I have bunged them both with ADP210 plugs.

Cheers, Paul

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1970 Morris Mini K

Hi all, thnaks for the responses. My carbs dont have the CCV ports, and Im after the original 'look' of the PCV - if I have to change it later, i'll cross that bridge then. What I need to know is, are the brake servo and PCV vacuum take off fittings the same? Or different sizes?
Cheers, Tom

These are as removed from my manifold. I cannot be sure that they are correct as a few things on the twins were also not right.



Note that the PCV fitting diameter is 0.48" as measured with verniers, but the equivalent fitting on the PCV itself measures exactly 0.5".

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1970 Morris Mini K

I agree with TDS76 on the size of the 2 original hose adaptors, although I have them around the other way i.e. larger one on the PCV, but likewise, can't guarantee they are as per original. The brake booster takeoff has a slightly smaller opening but both adaptors have the same 0.5" O.D. from the flare down.


Before you go drilling and tapping, I recommend you collect all the fittings for both ends of both hoses, as at least one adaptor is NLA and if using a VH44 booster, they have a smaller diameter (at 0.35") non-return valve than they used in 1970s.

I just checked the Tony Cripps book, and he has it the same way as Bill, so looks like mine were fitted the wrong way round.

Cheers, Paul.

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1970 Morris Mini K

Thanks all… sorted now


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