Vacum advance pipe

[ronnie]

hi all , the vacum advance pipe from manifold to dizzy ,, can anyone tell me the purpose of the egg timer object mounted on top of the thermostat housing , i kept the original metal pipe to keep it as authentic as possible . Will changing it to the modern plastic help in any way ?? .. Wee car M O T today with no advisorys,, taxed and on the road for the summer
ronnie

[Fingolfin]

Congratulations on being street legal! As to your question, well, isn't the thermostat housing and the vacuum advance on opposite ends of the engine? Which engine have you got?

[ronnie]

hi , its the 1098 engine . This little tubular part is half way along the pipe and anchoured by a bracket onto the thermostat at the front of the engine , i have no idea of its purpose or whether its something that could go faulty
ronnie

[bmcecosse]

I think it's supposed to trap any petrol - although why there should be any, and what it will do with it once trapped is beyond me.... Keep it or throw it away as you wish - but the important thing is to make sure the vacuum advance actually works!

[ronnie]

thanks for the info
cheers

[Alec]

Hello Ronnie,

is the part you are referring to an integral part of the copper vacuum pipe? I would have guessed that it is to help smooth out the vacuum itself, although the later plastic pipes did not have it?

Alec

[mike.perry]

It is a filter to stop petrol vapours from getting back down the pipe. It sounds implausible I know, but I've been there, seen it done it.
I had a Minor on loan whilst mine was off the road, I was driving along minding my own business when there was a small explosion from under the bonnet and the car stopped. Lifting the bonnet revealed a shattered distributor which was caused by petrol fumes getting back up the vacuum pipe and exploding when the points sparked

[Alec]

Hello Mike,

you said it :- "It sounds implausible I know,"

How can you filter petrol vapour and let air flow? After that the vapour has to pass the diaphragm, to the distributor, bearing in mind the flow is generally from the distributor to the inlet manifold (Even, I suggest at full throttle and no vacuum?). It does sound rather improbable, particularly, as I said earlier, the later plastic pipe doesn't have any device in it?

Alec

[bmcecosse]

The diaphragm must have been ruptured - but even then as you say Alec, the flow of air would be towards the carb....... I don't see any point in the bulb - faulty logic way back in the past I suspect and finally laid to rest when the plastic pipe was fitted.........

[ronnie]

every days a school day guys
ronnie

[mike.perry]

Sorry, should have clarified. It sounds implausible that vapour could get back to the distributor. I had a plastic pipe with no filter.