Vacuum Pipe from Manifold to Spark Advance

[TR3BGeorge]

Hello Folks,

 

First, I have ordered my BMIHT Certificate, so I will sit back and wait for it before I do anything re. my brass body plates.

 

I have had my car less than a month, and I took it to its first Red River Triumph Club meeting, to rave revues! Of course, they went over her with a pretty good eye. The first thing that was pointed out to me is that the vacuum pipe from the spark advance to the intake manifold is missing. This led to a discussion as to whether or not it is needed with my electronic ignition. Which also led to a discussion as to whether the missing line will affect my idle (which it does NOT), my acceleration, and my gas mileage. As expected, with 12 people discussing it, there were 12 knowledgeable opinions.

 

So, before I start buying parts, I contacted the PPO, who told me that it was on there when he sold it to the PO. So, I contacted him and he told me that he took it off when he put a Mallory distributor on the car, and left the Mallory on there for 2 years. When he decided to sell the car, he put the Lucas distributor back on, but no longer had the vacuum line.

 

For the replacement part, TRF was no help, as they don't have the pipe for the older cars. Moss was a different story. Of the 4 pipe/connector combinations, they stock two of them. The exact one I want they do not stock. But, I will be able to buy an adapter that fits into the manifold and accepts the pipe end fitting, and I will have to saw off the fitting at the distributor end as my spark advance has no threads on it and fits a short rubber hose that will fit the sawed-off end of the pipe.

 

One of the club members mentioned "testing" the vacuum first. I was discussing this with Don, who "tests" it the way we did back in the 1950s: suck on the tube and see if the plate in the distrubutor rotates. If it does, the vacuum element is alive and well. So, here is my question. How do YOU test the vacuum on your spark advance? In the old days, there was a vacuum tester, but I don't remember how it worked.

 

I have done a few small things, like adjust the handbrake and replace the chrome air cleaners with the original wire mesh cleaners. Of all things ordered, the decals for the air cleaners are the item on back order. Go figure.

 

As usual, I look forward to hearing from you.

[RAHTR4]

George,

 

You certainly do not need to butcher the vacuum unit to make it usable.

 

You can obtain all the correct copper pipe, brass olive and brass fixing nut from the Distributor Doctor :

 

http://distributordoctor.com/

 

He can answer any questions that you have and sort out any distributor problems and I do mean any.......!!!

 

Regards, Richard

[ianc]

Martin Jay (Distributor Doctor) will be at Malvern - look out for a big, bearded, fellow in a white coat. He is THE man for anything to do with distributors.

Ian Cornish

[james christie]

If I may add my Euros worth : A fair bet is that 50% of the vacuum arrangements on our TRs don't work anyway.

The theory is that the ignition is advanced when you put the foot down at low revs; without it there may be a very minor cough and splutter before the bob weights in the distributor take over.

After having my distributor weights expertly balanced - thank you Carl at Revington TR - I don't even notice that I ain't got my vacuum advance any more. Bliss - one thing less to break down, and yes I have electronic ignition

 

james

[ianc]

I feel I must correct Monsieur Christie's logic - too much vin de table, I fear, Jim!

 

There are three components to ignition timing:

- static setting

- centrifugal advance, controlled by the bob weights etc.

- vacuum advance (if used), which is additional to that provided by centrifugal.

 

The bob weights cause the ignition to be advanced as engine speed increases, but there is a limit to the amount of this advance. This operation is controlled by the springs, the weights and the cam, all of which are inside the distibutor.

 

When cruising at light throttle, the vacuum in the inlet tract will cause (via the diaphragm in the distributor) the ignition to be advanced further than the amount already given by the bob weights - this gives more economical running and, in particular, accounts for the TR2's spectacularly good mpg figures.

 

As soon as one depresses the throttle in order to accelerate the vehicle or or to maintain speed up an incline, the vacuum in the inlet tract is reduced and hence the ignition is retarded toward the level determined by the bob weights.

 

Fast road and competition engines usually have the vacuum advance disabled - by not connecting the pipe to the inlet tract.

 

Ian Cornish

[Ian Vincent]

I feel I must correct Monsieur Christie's logic - too much vin de table, I fear, Jim!

 

There are three components to ignition timing:

- static setting

- centrifugal advance, controlled by the bob weights etc.

- vacuum advance (if used), which is additional to that provided by centrifugal.

 

The bob weights cause the ignition to be advanced as engine speed increases, but there is a limit to the amount of this advance. This operation is controlled by the springs, the weights and the cam, all of which are inside the distibutor.

 

When cruising at light throttle, the vacuum in the inlet tract will cause (via the diaphragm in the distributor) the ignition to be advanced further than the amount already given by the bob weights - this gives more economical running and, in particular, accounts for the TR2's spectacularly good mpg figures.

 

As soon as one depresses the throttle in order to accelerate the vehicle or or to maintain speed up an incline, the vacuum in the inlet tract is reduced and hence the ignition is retarded toward the level determined by the bob weights.

 

Fast road and competition engines usually have the vacuum advance disabled - by not connecting the pipe to the inlet tract.

 

Ian Cornish

I agree with you entirely and in my youth (which was a long time ago) we used to call it a vacuum retard because that was its purpose - to retard the ignition when you accelerated and thereby prevent pinking.

 

Rgds Ian

[TR3BGeorge]

"VIN DE TABLE?"

 

God, I LOVE it when you talk dirty!