Mark Endicott wrote:
>
> I am in the process of installing a rebuilt set of SU's on my car and
> ran into a little problem. The vacuum line was attached to the front
> carbueretor on the originals. The rebuilts that I have don't have
> this port. I see that some earlier cars had the vacuum line attached
> to a port on the intake manifold. My manifold has a plug (screw) in
> this hole. Is there any reason not to connect a brass nipple to this
> port and use it for the vacuum advance?
Likely not the same.
The carb vacuum is probably ported vacuum, while the manifold
is (duh) manifold vacuum.
The main difference in use is that manifold vacuum is highest
at idle/cruise, and goes down from there.
Ported vacuum is near zero at idle, highest on strong
acceleration, then back down at cruise.
The ported vacuum is taken from around the throttle plate
in such a way that the throttle blocks it when closed.
If you switched to manifold, your timing would likely be
off especially at idle (or everywhere else if you set it
correct at idle).
--
Trevor Boicey
Ottawa, Canada
tboicey@brit.ca
http://www.brit.ca/~tboicey/
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