Barrie et al,
If there is a vacuum advance mechanism unit on the distributor and
your driving is mostly normal on the road activity, then connecting it up
is an advantage in my estimation. The idea is to cause earlier (more
advanced) timing at part throttle conditions and thereby improve fuel
economy. As the throttle is opened wider, manifold vacuum drops and the
advance falls back to only what the centrifugal mechanism provides and this
is in relation to engine speed only and has nothing at all to do with
throttle position. Under heavy throttle conditions, if all the advance
from both mechanisms was in effect, there could be a tendency to detonation
and pinging and possible engine damage. This is why all out racing engines
never use vacuum advance at all.
The connection to the carburetor needs to be to the correct point
on the base. I am not familiar with the carb in question but it is not
correct to go directly to the intake manifold. The port you want is in the
throttle body in such a position that it is shielded from the manifold by
the throttle butterflies at idle and progressively becomes more exposed to
the manifold as the throttle plates open. This produces very little vacuum
at idle, a lot at most part throttle conditions and nearly none at full
throttle.
You need to use vacuum hose. It is, as you say, more suck
resistant and does not collapse from the suction.
Therre is my 2 cents worth.
Cheers,
Dave Kernberger
----------------------------------------------------
I have an Edelbrock 1404, manual choke, and a standard Rover V8
>distributor with Pertronix on my Rover 3.5L V8. There is no vacuum
>connection between the two and as I did not do the motor bit I now wonder
>how this effects things. Can anyone help in this domain? If I do need
>such a connection is ordinary rubber tube suitable or do I need something
>with more suck resistance? Please accept, in advance, my many thanks.
>
>Regards
>
>Barrie Robinson
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