Vacuum advance pipe help

[sparkypete]

I have noted that there is a one way valve fitted in the pipe which runs from the pelnum to the advance retard on the dizzy.
Should this be there as when i suck on the pipe with it on the advance mechanism does not move, however if i remove it and suck on the pipe the advance moves.

Ant advise greatfully received.

[GreenV8S]

It's a slow return valve. If you take the throttle body end off and suck on that end of the pipe the vacuum advance should be very slow to move, it will feel as if the pipe is blocked. Disconnect the dizzy end instead and you will be able to suck through it.

The purpose is to stop the vacuum advance from kicking in briefly as you open the throttle from idle because it can upset the engine. However, the slow return valve is easily blocked and is routinely fitted back to front by people who don't understand it. In practice the problems that can be caused by the valve are far worse than the issue it is intended to solve, and if you're in any doubt I suggest you get rid of it and simply use a plain vacuum hose from the throttle body to the dizzy.

[Barkychoc]

I refitted mine as it seemed to be OK - it is marked on one side 'dist' and the other 'carb' you may need to scrape the oily gunge off to see the writing.