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Re: [T3] More Carb questions and theories


----- Original Message -----
From: "Ben Doughney" <ben_d@clear.net.nz>

> > Working to the "if the engine runs better its got to be better"
principle, I
> > have enriched the idle progressively to about 5 turns out on each and am
> > getting better mileage (but still only 20-22 mpukg) and a far smoother
> > running engine.
>
> That sounds a bit strange, my mixture screws are something like 2.5 turns
> out. Have you got a stock exhaust? If you had an exhaust with less back
> pressure than the original, that could possibly cause you to run too lean
> and need to compensate with the idle screws?

Hi Ben, what sort of mixture screws do you have- the later ones with a
little o-ring or the early with spring? They have different screw pitches so
I think that may make a difference to the "usual" settings. Mine are the
later finer threaded ones.

It is a stock exhaust in new a year ago condition. It even has a VW stamp on
it.

> What sort of distributor have you got? I get about 28MPG out of my '71
> Fastback, but it was a lot worse until I got the carbs synced spot on.
What
> about the balance tubes, do you have the late manifolds with the dual
tubes?

What sort of gallons are you talking there Ben? Mine are imperial which
equates to about 18mpg US- very poor! I must say though that 90% of my
driving is the same route to and from work which has speed bumps most of the
way so involves a lot of throttle and brake action. The best mileage I ever
got was a long run on the motorway which netted 26mp(uk)g

The distributor is the original vac advance unit that came with the car- it
has the correct part number but I can't remember what. The vac can holds
vacuum and advances. I had it apart and cleaned/re-lubed everything and it
was in good condition and all seemed to work fine.

Balance tubes are there- dual port type and all is leak free- I know about
it if one side comes disconnected!

I have the carbs as perfectly synced as I can get them using a very accurate
manometer between the intake manifolds on the balance pipe mounting tubes. I
double checked with a synchrotester and they tallied.

> It definitely seems puzzling, but it must be a part that you haven't
changed
> that is causing a problem somewhere.

Hmm I can't think of anything else. Its just strange and frustrating as it
otherwise seems so healthy.

Mark Seaton
'73 Fasty



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