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MG MGA - Routing of Vacum Advance Tube

I am installing a new Vac. Advance tube on my 1600 engine. I am attaching to Distributer then back and up where it fits in a clip on the back Head Stud then around back of head where it fits in a clap held in place by second from last exhaust Stud then ....? Does it point straight down and come up from under the Heat Shield to the carb port ( I have H4 Carbs )......thanks for any advice I can get or picture if possible........Tom
Thomas Koch

From the back cylinder head bracket it goes to the top of the flame barrier tube which itself is held in a bracket fixed to the second manifold stud from the end. Then from the bottom of the barrier tube it goes right to pass around the heat shield and then under the rear carb. to screw into the left hand side of the carb.
In the picture you can just about see the point where it screws into the carb. The vacuum tube makes a 180 deg. turn here.

I'm not sure whether this is original or not but it seemed the best way for me at the time..................Mike


m.j. moore

This picture shows it quite well.

Not my car. I have cheated and for easier accessibility I have bent the bracket so it attaches to the brass plate rear stud.

Steve


Steve Gyles

Thanks guys this helps a great deal ......
Thomas Koch

A supplementary question on this.

Considering head bolts are carefully tightened in order I have always been nervous about undoing the rear head bolt to just fit this pipes support hence tend to leave the pipe just hanging. Do others have this concern or am I just a wimp.

Paul
Paul Dean

On the rear stud, add an extra washer to stop the bracket rotating as you torque the head stud.
Art Pearse

Yes.. great advice Art .....that was needed with mine.
I think backing off the rear stud for a few seconds then torqued should be OK.
Thomas Koch

Art

Thanks, and useful, but my main point is that once a head is already fitted I am nervous on loosening and then tightening this one head nut out of sequence with other head nuts just to fit the pipe's clip. My issue only arises when you are working with the pipe away from fitting the head.

Paul
Paul Dean

Why not put the clip on top of the already tightened nut, then clamp with a thin nut on top? There looks like enough thread exposed to do it.

I have not bothered with that clip. It all seems quite stable. Been okay for 15 years.

Steve
Steve Gyles

There's not enough thread on mine Steve.
Art Pearse

I have often wished to do as Steve says but, like Art, I don't have enough thread. It would have been a good idea if it was made a bit longer. I suppose if i was having the head off I could get one made.

Paul
Paul Dean

It is tuff to get the clip to stop turning (kinking) while putting 50lbs of torque on that nut even with a washer and a little anti seize it wants to turn....

Why is it that you need to keep the fuel bulb upright on the Vac. tube have seen many with it on its side and routing it clipped to the back firewall.....as in this picture......Tom


Thomas Koch

It must be upright as shown in all the BMC publications.
If horizontal fuel vapour from the inlet manifold can condense and find it's way into the distributor.
The ignition points sparking and fuel presence in the Distributor is not a good idea. Very bad in fact.
Although in your photo the pipe from the bulb then goes vertical and so might be OK.

Mick
M F Anderson

The later advance tubes don't have a flame trap, and on my car I just use a rubber tube without any flame trap at all. The vacuum link has to be airtight or it won't work, and as the tube is under manifold vacuum it would be very strange indeed if the amount of fuel that could theoretically condense inside the tube to do anything more than blow the tube off its push-on fitting -IF- anything was to happen at all.
dominic clancy

Clipping to the firewall is definitely not a good idea! There is relative movement between that and the engine, which will cause the pipe to break.
Neil MG

This thread was discussed between 01/07/2015 and 07/07/2015

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