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Author Topic: Vacuum pipes - 1 spare?  (Read 303 times)
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JohnFol
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« on: March 26, 2022, 07:06:43 PM »

Really struggling with the carb this weekend ..  DATR

I need to check the vacuum pipes are correct and seem to have 1 too many pipes. Based on the reverlation the carb was missing an idle screw could someone sanity check my setup?
The inlet manifold has 1 connector  (ignoring brake servo pipe).
The carburettor has 1 connector
The distributor has a connector on the vacuum advance
The air filter box has 3 (1 for summer / winter flap) and 2 close together for what I think is a flame retard device in air box (brown thing with metal strip)
So 6 connectors that need linking up


2 vacuum pipes are straight through and 3 pipes are joined with a t-piece meaning I have 7 ends to connect.

7>6 so I know I have a problem.

I guess I have 2 main questions and possibly 1 answer. Have I missed a connector somewhere and how should they be connected?
 


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hutch6610
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« Reply #1 on: March 26, 2022, 07:46:46 PM »

Quote
The air filter box has 3 (1 for summer / winter flap) and 2 close together for what I think is a flame retard device in air box (brown thing with metal strip)
So 6 connectors that need linking up

Hmm a flame retard device how intriguing as i have never seen one. i suspect that what you describe is a thermostatic vacuum control valve for that summer winter flap which just controls the inlet air temperature (all year round)
The vacuum servo that operates the flap connects to one of the "tits" on the brown thing under the air filter box and the other connects to the nipple on the manifold. The thermostat has two little barbs either side to stop the pipe slipping off.
The pipe on the carb (cut off valve side) should connect to the vacuum advance on the distributor and there should be another that connects to the  breather - breather has a large pipe and a small pipe.
That should really be it. You may have a mixture of parts from different years? The car is not automatic is it?
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JohnFol
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« Reply #2 on: March 26, 2022, 08:44:12 PM »

Really appreciate the description and will have another look in daylight.
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JohnFol
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« Reply #3 on: July 25, 2022, 06:21:24 PM »

Car is a manual.
Flame retard is the wire mesh bit inside one of the pipes so my bad.
Carb has vacuum pipe to side rather than same side as cut off valve but I'm guessing it's the same thing.

So
manifold -> Vacuum Control Valve -> flap
Carb -> distributor -> breather

Got it
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JohnFol
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« Reply #4 on: August 12, 2022, 12:47:49 PM »

ok, getting close to a smooth running engine, however I still suspect an air leak as engine hunts.

The picture shows pipe from Carb (in red) to a T-piece. T-piece then splits into vacuum advance (blue) and air filter box / breather (green). This matches the description from hutch6610

However, blocking off the green pipe smooths out the idle (and that feels logical), so I'm after some reassurance / direction on where to go next.







* Carb Vacuum coloured.jpg (180.3 KB, 998x621 - viewed 52 times.)
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JohnFol
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« Reply #5 on: August 12, 2022, 03:34:45 PM »

tried it again after posting this and not as sure as I was earlier ..  .
Sad
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peteracs
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Peter Stokes


« Reply #6 on: August 12, 2022, 04:37:55 PM »

Hi John

Where on the air filter are you attaching it?

From what I can see the attachment on the thermostatic valve is a small bore pipe, not a large one like you appear to have.

Peter
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JohnFol
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« Reply #7 on: August 12, 2022, 06:07:02 PM »

This might be a better view. Left bit is the "green" small bore pipe and for contrast the big bore PCV pipe. The right of the picture is the connectors underneath the air filter box where the "green" pipe and PCV pipe are connected.

Interestingly, now the PCV pipe is exposed I see small puffs of air when engine running. Expected, but it feeds into the idea the engine hunting is a result of air/vacuum leak as the pulsing positive air pressure from the PCV is in very close proximity to the vacuum hose for carb<->distributor.


i.e.
Carb -> distributor only
manifold -> thermostatic control valve -> flap
             -> breather underneath air filter box (adjacent PCV big bore pipe)





* small vs large.jpg (78.78 KB, 630x376 - viewed 47 times.)
« Last Edit: August 12, 2022, 06:10:10 PM by JohnFol » Logged
peteracs
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Peter Stokes


« Reply #8 on: August 12, 2022, 06:25:35 PM »

Hi John

Just to clarify the green small bore pipe you have connected to the small bore pipe next to the larger vent pipe? Ie not to the thermostatic valve on the air intake?

Sadly my setup on the pre facelift is way simpler, but the small bore pipe next to the large vent pipe connects to the side of the base of the carb.

Peter
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JohnFol
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« Reply #9 on: August 16, 2022, 05:44:35 PM »

Working away from home so not able to double / triple check for a day or so however this the bit I can't get straight in my head

Air pressure in manifold will directly affect air/fuel mixture and advanced/retard via a vacuum pipe to distributor. Sticking a big bore pipe right next to it that pulses higher pressure from the crank must affect the vacuum and hence idling?

One last hmmmm moment. I have been reading up on PCV, and some have PCV valves that open/close e.g. https://en.wikipedia.org/wiki/Crankcase_ventilation_system. I've removed the PCV cover from the block, replaced the pipes, fitted new flame blockers, new clips, seals etc, but no sign of any valve. Should it have one?

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JohnFol
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« Reply #10 on: Today at 10:54:31 AM »

I may have found the culprit

Diagram shows pipe from PCV to airbox with a diaphragm labelled 34 and it's missing on my car.



* PCV.JPG (27.19 KB, 242x279 - viewed 10 times.)
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