Typically the vacuum advance functions only at times of high vacuum. That
would be like idle, or cruising at part throttle. It would not function
when you give full or nearly full throttle at higher speeds. It simply adds
a few degrees advance to the dizzy.
Timing is usually done with the advance disconnected and engine speed below
where the weights kick in to advance the timing.
A non functioning vacuum advance will only have a tendency to allow the
engine to run slightly retarded at those times.
Older vacuum advance units would give as much as 6 degrees advance, all the
replacements I've seen are in the 2 degrees range.
Some dizzys do not have a vacuum advance on them, such as the Cooper S
dizzy. All the advance is taken care of by centrifugal force by the dizzy
weights and springs.
Paul A
----- Original Message -----
From "Antony Gelberg" <antony at antgel.co.uk>
To: <spridgets@autox.team.net>
Sent: Wednesday, May 05, 2004 4:14 AM
Subject: vacumn advance
> If my vacumn advance wasn't working, would it cause a problem at idle or
> high rpm? Not that it has happened, as my car's still not running, but
> I noticed the vacumn lead was disconnected, and I don't think I did
> it.
>
> A
|