Thanks Don, for the advice.

Now here's the full story.  Any help will be much appreciated.

Having rebuilt the two SUs on my '54 120, I was unable to start the
engine from cold unless I used starting fluid in the intakes. Upon
examination of the starting carb, I determined it to be the non-
integral free standing type adjacent to the front carb, and
presented the viewer, looking down on it from above, with three
app. 5/16th inch diameter circular openings letting into 3 vertical
tubes cast in the body..

As I understood the workings, when the electrically operated
solenoid opened the small disc valve, this allowed the engine's
suction to draw in air through the jet/needle assembly via one of
these vertical intake tubes, causing an enriched fuel mixture to
enter the intake manifold, via the connecting tube.

It was apparent that all of the tubes were blocked as no air was
observed to be sucked in and, presumably, as a consequence, no
enriched petrol/air mixture entering the intake manifold to
facilitate the cold starting.

Upon dis-assembly, I discovered that there was no dirt of any kind
which might have blocked the flow of air. Indeed, upon closer
examination, I found that both the ''side'' tubes were never drilled
out in the casting, and that the ''central'' tube had been sealed off
with an aluminium stop plug. All three were sealed. Neither the
casting or the stop plug appeared to be any sort of modification
and could have been done by the factory.

I removed the plug in the center tube but, after some thought
decided against cross drilling the bottom of the casting in order
to allow more air to enter.

Upon re-installing, the car started from cold quite well, and the
air entering the ''central'' tube made a hell of a loud whistling
noise.

Has anyone run across this event before, and if so, could they
please explain how the carb would work with no ingestion of air
being possible.

I await your advices with bated breath.

Thank you.