Disconnecting the vacuum line from the capsule will introduce a vacuum leak,
which if the take-off is on the carb should do nothing at idle but if it is
on the manifold would cause the revs to rise. However the same manifold
take-off also results in max vacuum advance, so removing that pipe should
slow the engine, so I suspect you are getting no vacuum advance. Put the
pipe on the capsule and suck on it, see if it will hold a vacuum and
actually does alter the timing.
----- Original Message -----
From: "Warren Pruitt" <email@example.com>
Sent: Thursday, October 17, 2002 1:41 PM
Subject: Vacuum strangeness
> I was helping a friend tune his 74 roadster last night and we noticed that
> when you pull the vacuum line from the manifold to the distributor the
> engine speed increased. This is the reverse of what I have typically seen.
> His car had the twin su's and the mixture and synch seemed correct. Any
> ideas as to what causes this?
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