how much vacuum on the vacuum advance?

[kabaman]

Hmmm, I seem to be going round in circles here :-(

having recenlty replaced my vac advance unit on distie I had thought this was responsible for the cooler running (idling). Now I actually think this was simply becasue the statis timing was way too far retarded...anyway...

Putting the strobe on my 4.0 yesterday I noticed that as I connected and disconnected the vac advance tube it made no difference to the advance at idle. But...sucking the tube (no comments please) advances the timing. Disconnecting the tube from the manifold and blowing (no comments please) suggests that this path is clear. So it seems like:

1) There isn't enough vacuum on the I/L side although it idles reasonably ok

or

2) The vac advance is not matched to the amount of vacuum I actually have.

Any ideas any one?

One thing...the vac take off from the plenum has some araldite around it so someting's happened to it in the past but it seems ok in terms of the fixiing and the fact that I can blow through it.

Cheers,

Neil

[GreenV8S]

Since your vacuum take-off has been modified I can't be sure it's connected to the standard place, but assuming it is then it will be a ported vacuum connection. This means it is connected to a tapping which is lined up with the throttle plate so it is upstream when the throttle is fully closed (i.e. at idle) and downstream when you crack the throttle open (light throttle cruise conditions). In this case you would not expect to see the vacuum advance operating at idle.