Vac advance question for RV8

[zippy500]

Investigating a low rpm flat spot on my car. With the vac unit removed, should I be able to suck on the pipe and see the little arm move inwards?
Suspect it's only a small movement anyway, but I cant see any movement at all.
The weights all seem to move freely.

Have eliminated the throttle pot as a cause as tried anothe rone and it was no different. So dizzy was next port of call.

Also, when turning the weights by hand, should they spring back or do they totally rely on centrifugal force to move them?

Thanks

Edited by zippy500 on Saturday 16th May 13:16

[GreenV8S]

If you suck on the vacuum port, it should hold pressure. If it leaks, it's failed. When you suck it should also pull the arm in. I haven't had one fail so that it holds pressure but doesn't move, but I guess it's possible.

[mdotrutherford]

Lots on this only recently

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

HTH

[eliot]

mdotrutherford said:

Lots on this only recently

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

HTH

Good thread - just ignore the bit about "upgrading" to a mallory unit though. The only thing they upgrade is a certain norfolk sellers bank balance.

[rigga]

GreenV8S said:

If you suck on the vacuum port, it should hold pressure. If it leaks, it's failed. When you suck it should also pull the arm in. I haven't had one fail so that it holds pressure but doesn't move, but I guess it's possible.

I have.... the first one i purchased from rimmer bros did exactly that,sent it back and they returned a working unit,made a noticable difference when fitted compared to my original duff one which had a split diaphram and wouldnt hold vacumn