Manifold vacuum decreases as your throttle plate opens. The dizzy wants full
advance at full throttle. if you use carb vacuum,the dizzy gets an
appropriate indication of the engines running demands otherwise, you get
less advance at full throttle, and more at idle . just the reverse of what
you relly want.
Mark Haynes
'62 Sprite XSP motor
> -----Original Message-----
> From: Richard Shipman [SMTP:mbelect@mindspring.com]
> Sent: Wednesday, August 04, 1999 7:28 AM
> To: John MacDonald
> Cc: spridgets@autox.team.net
> Subject: Re: Timing the 1275 ? (vac. advance with a sidedraft)
>
> I don't understand... If the vacuum advance on my '74 Midget works with
> manifold vacuum, why won't manifold vacuum work with other
> configurations??
>
> Richard
> '74 Midget
> '68 MGBGT
> '58 Morris Minor
>
>
> >Variable vacuum. At the manifold it is 100% vacuum providing 100%
> advance
> >all the time. Just before the throttle plate it is variable.
>
> >
> >>Can anyone explain to me why my '74 Midget with SU's has a simple vacuum
> >>advance fitting right on top of the intake manifold and yet so much care
> >and
> >>attention is being taken to locate the vacuum pick-up at a specific
> point
> >on
> >>a sidedraft weber??
> >>
> >>What am I missing??
> >>
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