> It has been fitted with twin SU HS6's which in itself is no big
> problem, but
> the vacuum port is on the bottom of the front carb, and seems to be
> controlled by the position of the butterfly disc. I think this
> means it is a
> vacuum retard port. Are vacuum advance ports controlled by the butterfly
> disc
Both retard and advance ports are controlled by the butterfly. The advance
port is on the side where the butterfly sweeps towards the piston as it
opens, the retard port is on the side where the butterfly sweeps towards the
engine. For an HS6, that means the advance port is on the top and the
retard port is on the bottom.
> My question is, is this a problem for a car fitted with a vacuum
> advance?
IMO, yes. You'll get no advance when you need it, and lots of advance when
you don't.
The engine will still run fine (after you deal with all the other problems),
but will burn more fuel when cruising. My experience has been that a
working vacuum advance also improves part throttle response, but it's tough
to notice unless you've just fixed it.
Randall
|