Depends where it is supposed to be. Carb port is best, and you will be
losing both performance and economy if not connected. Manifold connection
became the norm in North America at some point, moved from the carb,
probably due to emissions considerations. Still improves
performance/economy when connected but not as much as carb connected. Some
of the latest North American MGBs had a vacuum connection even though the
points plate was staked down. This is because each car was tested and some
could only pass the emissions tests this way.
Carb connected has no advance at idle, increasing advance as the throttle is
opened up to a certain point, then decreasing advance as it is opened
further. Manifold connected gives maximum advance at idle and decreasing
advance as the throttle is opened. Both are about the same when cruising
and full-throttle, but very different at idle. Increasing the timing to max
when cruising gives best economy, reducing it at large throttle openings
prevents pinking.
PaulH.
----- Original Message -----
From: Gordon Bird <gb@the-bdc.com>
To: list MG (E-mail) <mgs@autox.team.net>
Sent: Friday, September 15, 2000 8:00 PM
Subject: vacuum advance
> I'll be helping my neighbor time his 70 B this weekend and I noticed that
> the advance from the dizzy is not hooked up. Upon looking at other
similar
> years I find some are and some are not hooked up.
> What effect does this have on the timing, if any?
> Any reason for this to be reconnected?
> TIA
>
> Safety Fast!
> Gordie Bird
> 62 MGA
> 80 MGB
> 86 Audi 4kq
>
>
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