Vacuum pipe fittings

[anotheralan]

Having sorted the mixture on my 87mm TR3 (many thanks again to those that helped) my attention has turned to the vacuum pipe and its fittings. I do get some wetness collecting in the clear plastic u-tube i have used to connect to the new distributor, which acts as a 'trap' a bit like a household sink trap. I am considering replacing the original metal pipe (untrapped) with a new cylinder trapped type, but not sure why/whether this is really necessary.

Background is that the car was an early lo-port TR3 but I replaced the head with hi-port and 302119 hi-port manifold and the original H6 carbs retained.

The vacuum pipe is ,as I said above, the original without trap and female fittings at both ends (201875 pipe & AUC4490 adapter at carb end).

All trap type pipes have male fitting at carb end. I am not sure whether simply removing the adapter will allow the male fitting to attach directly to the manifold or whether i need to replace the carb end pipe fitting with a female fitting and olive?

I thought of using 12H733 trap type as HS6 carbs and reversing the ends but suspect that may put the trap in a place where supporting might be a problem and i understand the trap must be vertical and the right way up. I am not sure how the trap is constructed inside but I take this advice to be correct.

Hoping for the usual excellent input.

Alan

[Richardtr3a]

Just fitted one on my 3A because there was petrol in the vacuum diaphragm. I changed the end to fit the adaptor because the male fitting will not fit direct into the manifold.

 

Mu mpg has risen dramatically. My kit from 1H919 Moss had have the additional fitting and a new olive. It comes with a small bracket which I bent through 90 degrees and attached it to the thermostat housing. NB lower end of vertical trap to carbs.

 

I never had one before but it has made a difference.

 

Good luck Richard

[TomMull]

I can't see any reason that bulb would do any harm and if it eliminates petrol in the distributor, that would be a good thing. But my 1959 TR3A has been in at least limited commission ever since it was new and has never had a trap.

Tom

[Fireman049]

Tom.

 

[David Edwards]

Sorry chaps , but I too am battling with vacuum pipe issues. Should the vacuum pipe with the trap be fitted such that the trap functions in a certain direction? Is it a trap that can work in either direction or does it a have a one way valve function and is therefore directional.--reference Moss 12H733. vacuum pipe.

David.

[billy l]

Hi David, it can only be fitted one way round, the union fitting connects to the carbs and the push fit connects to the advance/retard. Cheers, Bill.

[RobH]

Sorry chaps , but I too am battling with vacuum pipe issues. Should the vacuum pipe with the trap be fitted such that the trap functions in a certain direction? Is it a trap that can work in either direction or does it a have a one way valve function and is therefore directional.--reference Moss 12H733. vacuum pipe.

David.

There's nothing special about the 'trap'- there are no valves in it, basically It's just a bottle and can work in both directions. The function is to provide a cold point (colder than the source anyway) where any petrol vapour can condense into liquid and run back towards the carbs, so it makes sense for the bottle to be as far from the manifolds and carbs as can be arranged. Since it is not used on all models it's arguable whether it is necessary anyway, as those cars without seem to run perfectly well. Some people describe it as a flame trap but I don't believe that at all, as even if full of fuel vapour the small-bore pipe would not sustain combustion. (Ref. Davey Lamp for explanation of that).

 

Richard's gain in MPG (post 2) probably has nothing to do with the trap but everything to do with getting a good vacuum connection to the carb advance mechanism.