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Is This Ccv Setup Correct?

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#1 DamoMini


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Posted 16 November 2019 - 07:56 PM

Have read through as many posts as I can over the last two nights and I'm still not 100% sure that this is correct.


The car is a 1978 Mini 1000 - I have had it about a month.


Car starts and runs fine. It idles okay at around 900-ish RPM. I have been using it as a short commute vehicle. No worrying oil leaks apart from tiny amount of "seepage" keeping the floor rust free.


I am about to embark on some routine tune up items (valve lash, then timing, then carb adjustment).


The breather hoses are old and perished in spots so I am going to replace them before the tune up but before I do I would like to confirm that the CCV circuit is correct - I have no idea if the system was modified previously.


Current components are an aftermarket rocker cover with a breather pipe, a vented oil filler cap, and a breather/can exiting the timing chain end.  No breather on the clutch end.  Carb is HS4 with a K&N pancake/cold intake type air filter attached directly to the carb.


A hose from the rocker cover breather port is connected to a T joint where it meets the hose from the timing chain side breather.  The T is then connected via more hose to the carb at a point that sits between the piston and the throttle valve.


This seems correct for a CCV setup but I am wondering what the airflow path is, particularly given that the rocker cover is both open to the atmosphere (vented oil cap) and connected to the breather circuit.  Does the crank case gas under pressure splt itself between the carb and the rocker cover?


Thanks in advance,



Edited by DamoMini, 16 November 2019 - 07:57 PM.

#2 Dusky


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Posted 16 November 2019 - 08:20 PM

Its correct.
Carb pulls air through the rocker cover cap into the engine/into the breather hoses/into the carb. Creating a slight negative pressure.

#3 unburntfuelinthemorning


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Posted 16 November 2019 - 09:16 PM

And when the engine's worn out with huge amounts of blow by what isn't sucked into the carb will exit via the filler cap.

#4 DeadSquare


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Posted 17 November 2019 - 12:03 PM

And when the engine's worn out with huge amounts of blow by what isn't sucked into the carb will exit via the filler cap.


And at that stage, you don't need petrol, as it will run on hot oil fumes.  :D

#5 cal844


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Posted 17 November 2019 - 12:05 PM

On my 89 998 it doesn't have the rocker cover ccv port

#6 Moke Spider

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Posted 17 November 2019 - 05:40 PM

Damo, that set up will work, in part.


The original set up drew from lower down in the Crankcase, and not off the Rocker Cover.


This was so there was a continuous 'air' flow through the Crankcase to stop moisture building up in the Oil. Drawing off the Rocker Cover by-passes this.


I would suggest disconnecting that Hose and blanking it off, drawing only from the Timing Chain Cover.


Also, many Vented Caps I've seen on Alloy Rocker Covers don't have filters in them. Just be mindful of that if you drive in dusty conditions.

#7 DamoMini


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Posted 17 November 2019 - 06:06 PM

Thanks for the input. I am really happy to hear the suggestion to cap the rocker cover hose as this piece of the setup was bothering me.

My oil filler cap has wire mesh at the bottom but I can’t see if there are additional filter materials packed in there. I should probably get a new one as this is supposed to be a service item.

“I wish” on the alloy rocker cover! It’s more like a chromed steel jobbie and the chrome has started to blister in spots. I see a paint job in this part’s future.

Thanks again.


Edited by DamoMini, 17 November 2019 - 06:07 PM.

#8 Ethel


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Posted 18 November 2019 - 01:41 AM

Small bore A's usually had an oil separator on the tappet chest cover nearest the fan.

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