Air filter replacement

[RobH]

Item 30 here but you will 31 and 22 as well, fo H6 carbs. That is assuming the vacuum pipe you have now is the right diameter of course, if not either they won't fit or the olive won't seal.   Might be safer to also buy the correct pipe while you are at it but the 21 pipe has the wrong fitting for the dizzy. You would have to cut the olive off and use a rubber pipe (27) to connect the two. I don't know whether the 25 pipe will accept the nut and olive - I suspect it will. 

https://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/electrical-system/ignition-system/ignition-system-tr2-4a-1953-67.html

Edited October 6, 2023 by RobH

[stuart]

41 minutes ago, Smithfire67 said:

What's an Olive Stuart?

Its a hollow brass fitting shaped as name suggests to go over the pipe so when compressed by the nut its squeezes up to provide a seal. See item 30 here https://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/electrical-system/ignition-system/ignition-system-tr2-4a-1953-67.html

Edit Rob beat me to it.

Stuart.

Edited October 6, 2023 by stuart

[Smithfire67]

1 hour ago, RobH said:

Item 30 here but you will 31 and 22 as well, fo H6 carbs. That is assuming the vacuum pipe you have now is the right diameter of course, if not either they won't fit or the olive won't seal.   Might be safer to also buy the correct pipe while you are at it but the 21 pipe has the wrong fitting for the dizzy. You would have to cut the olive off and use a rubber pipe (27) to connect the two. I don't know whether the 25 pipe will accept the nut and olive - I suspect it will. 

https://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/electrical-system/ignition-system/ignition-system-tr2-4a-1953-67.html

Yeah, the vacuum unit I have is attached to the brass tube with a rubber pipe.....

[Smithfire67]

On 10/6/2023 at 3:20 PM, stuart said:

Its a hollow brass fitting shaped as name suggests to go over the pipe so when compressed by the nut its squeezes up to provide a seal. See item 30 here https://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/electrical-system/ignition-system/ignition-system-tr2-4a-1953-67.html

Edit Rob beat me to it.

Stuart.

Hows about this Stuart? 

[stuart]

That should do it, the fitting under the carb does need to be correct which hopefully that one is as there are two different ones Ive seen fitted over the years.

Stuart.

[Smithfire67]

38 minutes ago, stuart said:

That should do it, the fitting under the carb does need to be correct which hopefully that one is as there are two different ones Ive seen fitted over the years.

Stuart.

Cool. Any idea what the little valve is on the pipe? 

[RobH]

If you mean the bulged section - as I explained before it is a vapour trap intended to stop petrol vapour condensing in the dizzy.  That bit needs to be mounted vertically for it to work properly - see the photo in this old thread.     

 

[Smithfire67]

1 minute ago, RobH said:

If you mean the bulged section - as I explained before it is a vapour trap intended to stop petrol vapour condensing in the dizzy.  That bit needs to be mounted vertically for it to work properly - see the photo in this old thread.     

 

Ah thanks Rob. 

[james christie]

I’ve been running my 3A without the vacuum unit for some 20 years now. Of course with all the orifices blocked off.  I don’t notice its absence (maybe I should)

Something less to go wrong!

james

[RobH]

It only affects fuel economy in the cruise when the throttle opening is small James,  so you wouldn't notice it while driving. 

 

 

Edited October 7, 2023 by RobH

[Z320]

deleted

Edited October 7, 2023 by Z320

[Smithfire67]

42 minutes ago, Z320 said:

deleted

 

1 hour ago, RobH said:

It only affects fuel economy in the cruise when the throttle opening is small James,  so you wouldn't notice it while driving. 

 

 

I'd like to get my car back to the original state by re fitting this. 

[RobH]

35 minutes ago, Smithfire67 said:

I'd like to get my car back to the original state by re fitting this. 

And rightly so.  The way yours was connected and the absence of any closure of the carb drilling  would definitely affect performance, whereas in James' case the complete absence of the pipe and a closed-off hole would just affect economy. 

 

Edited October 7, 2023 by RobH

[Z320]

Hi all,

I can‘t find a matching explanation for the need of the trap in the vacuum pipe and how it works.

On my TR4A is no trap in the copper pipe and this works. Why not?

Because I‘ve been told a lot of not matching stories I had a closer look on the advance unit some years ago.

With a gauge connected, the pipe correct connected and not connected.

After a 2 x 100 km tour on fast country roads I was convinced about it’s benefit.

My advice: test it and come to your own conclusion.

Ciao, Marco 

Edited October 8, 2023 by Z320

[RobH]

33 minutes ago, Z320 said:

I can‘t find a matching explanation for the need of the trap in the vacuum pipe and how it works.

Neither can I Marco.   Later BMC cars just used a plain plastic vacuum pipe so whatever the reason for the trap was, it must have been dismissed. 

[stuart]

On 10/8/2023 at 9:44 AM, RobH said:

Neither can I Marco.   Later BMC cars just used a plain plastic vacuum pipe so whatever the reason for the trap was, it must have been dismissed. 

Introduced on MGB models I believe.

Stuart.

[Charlie D]

On 10/8/2023 at 9:07 AM, Z320 said:

I can‘t find a matching explanation for the need of the trap

There must be some sort of diaphragm inside the distributor vacuum capsule “Thing”.

I wonder if earlier versions had a diaphragm made out of a material that could be attacked by petrol, hence the need for a vapor trap. If the material was changed later on to a type that could stand petrol vapor then maybe that is why the vapor trap was no longer needed.

That’s my theory, anyway.

Charlie

[Z320]

The inlet manifold sucks on the vacuum unit.

How should fuel vapours go there?

What to do if they are trapped in there?

How do I know?

[Smithfire67]

16 minutes ago, Z320 said:

The inlet manifold sucks on the vacuum unit.

How should fuel vapours go there?

What to do if they are trapped in there?

How do I know?

I don't know.....but I'd love to find out!

[Charlie D]

24 minutes ago, Z320 said:

...The inlet manifold sucks on the vacuum unit...

 

The inlet manifold sucks on the vacuum unit.
Only when the engine is running.

How should fuel vapours go there?
With the engine off fuel could come out of the jet (if the float is not adjusted correctly.) and into the vacuum pipe. This fuel will vaporize because the pipe is hot.

What to do if they are trapped in there?
They will eventually condense back into petrol and run back into the carburetor.

How do I know?
I’m not claiming that what I say is true.

Maybe I just have an overactive imagination.

Charlie

[Z320]

Good to know I should have worries about problems I never had

[stuart]

FWIW The 123 unit that does have a vacuum advance recommends a trap in the advance pipe as they say the unit can be damaged without.

Stuart.

[Z320]

57 minutes ago, stuart said:

FWIW The 123 unit that does have a vacuum advance recommends a trap in the advance pipe as they say the unit can be damaged without.

Stuart.

Yeah I know,

I always wondered what to do when the trap ist full....

 

[BlueTR3A-5EKT]

46 minutes ago, Z320 said:

Yeah I know,

I always wondered what to do when the trap ist full....

 

Would manifold vacuum not empty it when the throttle is closed?

[RobH]

29 minutes ago, BlueTR3A-5EKT said:

Would manifold vacuum not empty it when the throttle is closed?

No Peter.

 When the butterfly is closed the hole is covered so there is no vacuum in the pipe and in any case there is virtually no flow through the pipe to carrry away condensate even with a vacuum. 

You would have to unplug the pipe from the dizzy occasionally, and run the engine at above idle speed to suck air through the tube and hope it takes any condensate with it .