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Mk 1 Frogeye Vacuum Advance

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ARennie

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I am trying to sort out a 1959 Frogeye Sprite (948cc) owned by my Fiancee. This vehicle was originally owned by her mother and has been subjected to a 'commercial' restoration which leaves a bit to be desired. One of the issues I am trying to resolve is the vacuum advance. When I first got the vehicle going it was missing at about 3500 rpm and I soon found that the manifold end of the vacuum advance tube was not connected to anything!! I have hunted high and low around the twin SU carbs and the inlet manifold but there seems to be no tapping or tube for this to connect into. I have obtained the original BMC workshop and parts manuals and they shed no light on the issue. The workshop manual simply says disconnect the vacuum tube! The parts manual shows the tube with a connecting nipple but does not show where it connects into. The exploded view of the Carburettors and the inlet manifold also shed no light on the mystery! The manifold appears correct the only possible hint that there is is that the parts manual refers to two SU carb bodies a 1 and a 1a but does not say what the difference is. It could be that during restoration two of the same have been used. As it is the vacuum tube is copper and comes from the distributor around the back of the tappet cover where there is a small copper chamber like an accumulator in line, it then continues and ends just by the aft of the two SU carbs.
Can anyone tell me where the connection should be? The ideal would be a photograph. If I need to purchase the correct parts I am happy to. It has been suggested that I just drill and tap into the manifold and insert a connection, I do not feel that this is an option even though I have no doubt it would work. I would rather get the vehicle back as close to original spec as possible, it has had one owner since new and that must be somewhat unusual.
 
I would think the engine should run fine without the vacuum advance (just poorer fuel economy).
 
You should find the vacum advance port on the front carb, rear side kind of close to the manifold.

Check the rear carb as well, maybe some PDO got them on backwards.
 
Here it is an an HS2, not that would apply much to a Bugeye. I asked over the weekend as I wondered if this were ported or manifold and I guess it varies, so just tapping the intake for a source of manifold vacuum may not be best solution. The vacuum line to the dizzy may not be vac advance but a vac retard or something.
vac advance port.gif
 
If the bowls on your carbs don't look like the ones in jvandyke's picture and instead have a nut at the top for the fuel line connection and brass damper nuts they are HS1 not HS2. In that case the port for the advance is where Jack says it is. It is on the right side of the front carb and slightly underneath. Very hard to see with the carbs in place, but you might be able to find it with your finger.

Brian
 
Thanks everyone. This is really a great help. I cannot get my hands on the vehicle till next weekend but will report back once I do.
Thanks again
Alick
 
H1: front carb, right side, just behind the flange that connects to the manifold. There should be a little brass tube pointing down at a 45-degree angle.

If it's not there, it may have fallen out. It happens. (For example, to mine!) Or, since you have copper vacuum line, maybe it uses a fitting instead of the tube. You might have to take off the carburetor to see it clearly.
 
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