>I had my mechanic rebuild my carbs to eliminate a rough sputter when
>pulling away from a stop. The sputter was said to be caused by lean
>carbs that could not be adjusted anymore due to worn metering needles,
< snip >
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I hate to disagree with a mechanic in which you apparently have confidence
with, but either you misunderstood him, he wasn't clear as to what he was
trying to say, or he is, well, sorry. ..incorrect. Worn metering needles,
and/or the orifice in which they operate CANNOT cause the mixture to become
leaner, only richer. If the metering needle hole (jet) is worn [larger]
and/or the metering needle is worn [thinner] then the cross sectional area
that fuel flows through is also larger at the same pressure drop (same
amount of air passing through the jet/needle/Venturi area) as when the
jets/needles were not worn. A larger fuel opening equals more fuel (with
the same amount of air). Therefore, if indeed you have worn needles/jets
then if anything, you would not be able to adjust the mixture LEAN enough.
The problem would be of having too RICH a mixture, not a too lean one. If
the stumble is TRULY caused by a lean mixture I.E. not enough fuel at
immediate throttle openings, then look to the dampers for proper oil level,
or a vacuum leak somewhere.
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>etc. Prior to the rebuild, he made a temporary adjustment to the carbs
>by grinding off a very slight amount of the head (opposite the point) of
>the metering needles.
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I'm not absolutely sure as to what you are referring to here. There isn't
anything referred to as a "head" in reference to a carburetor. At least
not that I am aware of, and all I can visualize would be the end of the
needle itself. Specifically, to the part of the needle that would be
inserted into the damper piston. If that's the case, then your problem
lies somewhere else, not in the carbs per-say Making modifications of this
nature in an otherwise stock running engine is NOT the way to fix the
problem (I am assuming that the engine is stock or was running fine before
this stumble, and subsequent repairs were started) It may mask it, but
there is obviously something else wrong -
Barry Schwartz (San Diego) bschwart@pacbell.net
72 FI, V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire (long term project)
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