Vacuum Advance Tube

Where do you guys have your VA tube connected to your manifold? On which orifice specifically. Does it matter?

It doesn't matter.

I am also a recent 1972 MGB roadster owner. When looking at my Dissy the vac pipe has gone missing, I believe I have emission pot fitted. I have checked all around the inlet manifold, and canot see any obvious take off for the Vac / advance.

Hoping you may help.

I believe this is it for a twin SU carb set-up...

On hif carbs it goes to rear card ...and it DOES matter whether your dizzy is set up
for ported /or manifold pressure.

Actually, from 1970-1975 the vacuum advance was attached to the rear most port on the intake manifold. From '76-80 (I think) the TCSA was used in all cars, so manifold vac was supplied to the switch, and the distributor was attached to the switch as well.

On cars with a Zenith, you cna actually install a vacuum Tee at the EGR port and use that signal for the vacuum advance if your TCSA has failed. It will perform better than using direct manifold vacuum.

Yes the TCSA system is ported towards the front of the manifold on my 79. The swtich is activated in fourth gear but according to John Twist is worthless. My aft port is used for the brake booster.