Hey Rex,
Thanks for the reply. I've held the engine at higher rpms and put my finger
over the brass vacuum advance port (which is located on the carb) and still
felt no vacuum whereas the manifold line pulls hard even at idle (which I
would expect due to the drastically different cross section of the
openings). Do you have any recommendations as to how I might clean through
the very small hole of the brass vacuum advance port?. I imagine that I'll
soak the carb body in laquer thinner overnight and then try to use pressure.
Currently, because vacuum to the advance is more important than retart I've
got the manifold vacuum line (normally the retard) running directly to the
advance unit (id est bypassing the vacuum switch on the throttle bellcrank)
and the distributor set static; my motor runs great. But I'd like to
eventually get everything running as original. I'm also concerned about
having too much vacuum on the vacuum advance unit and ruining it.
Sincerely,
Dave Herbert
>From: "Rex Townsend" <rrt@connectexpress.com>
>Reply-To: "Rex Townsend" <rrt@connectexpress.com>
>To: <6pack@autox.team.net>
>Subject: brass vacuum fitting on top of carb
>Date: Wed, 28 May 2003 06:20:12 -0700
>
>Dave and Steve,
> No, there is nothing wrong with your carb because it shows no vacuum at
>the
>brass vacuum advance port when you check it with the engine idling. This
>port doesn't get vacuum until the throttle is at least part way open.
>These
>1969 cars had both vacuum advance and retard, and the retard unit was
>actuated off of manifold (rather than carb) vacuum. There is a vacuum
>switch on the throttle bellcrank that opens and closes the vacuum line to
>the retard unit, so that the spark is only retarded when the throttle is
>closed (at idle or coasting). If the advance unit were also getting vacuum
>at this time, the two vacuum units would be "fighting" each other, probably
>resulting in neither advance nor retard. Once the throttle starts to open,
>the vacuum switch shuts off vacuum to the retard unit, and the vacuum port
>in the carb starts delivering vacuum to the advance unit.
>
>Rex Townsend
>CC26713L
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