[T3] More Carb questions and theories

["Mark Seaton" <mark.seaton2@ntlworld.com>]

Hello all,

My fasty is running great at the moment- really smooth most days but I'm
still getting lousy gas mileage.
The carbs are stock Solex re-built/NOS so I believe them to be OK and I've
been through a few of them to no avail. I'm pretty sure that there are no
vacuum leaks, the dist is fine and there are no fuel leaks. The jets are as
specified stock for a '73 1600. I'm beginning to think that there is
something more fundamentally wrong/amiss.

The engine seems very healthy otherwise but I don't know much of its history
save that its the original case registered with the car from new. I'm
getting 120-130 PSI on all cylinders with 3 lowest. Milo says about 40k but
seats say different.

Problem is that if I go by the book regarding idle jet adjustment (1.5 turns
out or so) I get stinky exhaust and low power and even worse mileage.
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.

On the CO meter this is very poor- 10% or so, but if the engine is revved it
drops below 1%. It is obviously rich as the plugs are pretty sooty. But it
drives better!

So here are the questions/theories;

1: My engine might not be stock- perhaps I have more than 1600cc! I don't
know this and didn't check when I had the chance ;-( Would a too small main
jet cause such poor fuel consumption? It seems like I might be compensating
for too small a main with too rich an idle but surely that is limited by the
idle jet/cut off valve?

2: Does modern petrol require different jetting for optimum results- Perhaps
I need bigger main jets anyway with today's poorer quality petrol?

3: Is it possible that the emulsifying tube for the main jet is
faulty/blocked/corroded and reducing the effective jet size? These are not
very user serviceable so I don't know what to do if this is a possibility.

4: Where can I get larger main jets preferably in the UK?

TIA for any ideas or suggestions,

Mark Seaton
'73 Fasty


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