On my 2.1 L, 91 syncro westy, I recently changed from
a gerry rigged bug manifold and a bug Solex carb to
the proper VW European (Pierburg carb) manifold intake
and a NEW Weber DEFV (or DFAV) single (2 barrel
progressive) carb.  While this may not be on topic for
your dual carbs, I can tell you that what I know.

Initially the carbs were jetted WAY to rich, I kept
putting in leaner jets, both air and fuel (I bought
the jet kit) till the plugs stopped going black in 100
miles.

My MPG went from about 19 mpg (with the Solex) to
about 16 mpg with the Weber,  As I leaned the carb
out, MPG went up to 17-18 mpg.  This driving was on a
trip from Michigan to Calgary to Nova Scotia - all
highway driving, but at altitude and hills/mts &
loaded.

Also I can tell you that with the present set-up, The
van runs better than it has every run. truly amazing,
it pulls from low revs up to higher revs effortlessly.
 And it ran without a miss from 9,000 foot passes to
sea level (as I changed jets).

One caveat is that in Nova Scotia we do NOT have
pollution testing, so carbs may not be legal in your
state/Provence.

Also my experience is from the gerry rigged Solex to
the proper manifold & Weber, NOT from FI to Carb. (my
van lost its FI in the PO's fire).

I will not try dual carbs as I have been told that I
will spend half  my life balancing the carbs

I'm still in the process of playing withthe jets to
get the Right mix of power and economny, I prefer
economy.

I hope some of this helps.  Malcolm

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