[Fot] Spitfire mixture needles

[Greg Solow]

Regarding the Spitfire. There are no vacuum leaks. The PCV valve is ok. We
have not checked the cam timing. Maybe that is in order. The engine runs
GREAT!  with the DK needles installed. What we really need is a chassis dyno
to check mixture under load. There used to be one in San Jose but it is no
longer in action. Maybe a "Smog test Dyno" might work? Has anyone tried one of
these for tuning as opposed to Smog Testing?
                                                                             
               Greg Solow
  ----- Original Message -----
  From: EDWARD BARNARD
  To: Greg Solow ; Friends of Triumph
  Sent: Tuesday, October 30, 2007 8:51 PM
  Subject: Re: [Fot] Spitfire mixture needles


  Greg: Perhaps this suggestion is too simple, but, have you checked for
manifold air leaks that would cause the mixture to be lean because your
sucking air? Could be your adding extra air after the throttle plate; carbs to
manifold, manifold to head, hose from manifold to PCV valve bad. Just silly
things you've probably checked already. - Ed

  Greg Solow <gregmogdoc at surfnetusa.com> wrote:
    We have been working on a 1968 Spitfire Mk 3, It is a stock, very
origiinal
    car. We have just done a valve job, installed hard exhaust seat and new
    guides, & replaced the rings. The compression is great and the engine is
nice
    and tight. It has the stock tubular headers that cam on this year car and
the
    dual 1 1/4" HS-2 carbs.
    We are having a tuning problem. With 2 psi fuel pressre at the carb at
WOT
    the engine runs lean, especially at part throttle. The stock spec. calls
for
    "DD" mixture needles. They are way lean. Just bringing the revs up from
idle
    to about 2500 to 3000 rpm with no load the engine spits and runs very
rough.
    Adding fuel makes the engine "rev" right up. We have tried progressively
    richer needles going from the "DD" to "AN", then to "H-6" and finally to
"DK"
    needles. With the "DK" needles installed the engine runs"GREAT' under any
    circumstances
    but I am afraid that it is to rich. I took it on a 35 miles or so road
test on
    Sunday with these needles installed and it was a pleasure to drive! but
seemed
    to just "suck" gas, but this is a subjective judgement as I was not able
to
    measure the fuel economy. Note, the cam, displacement, etc. are all stock
in
    this car. I am at a loss to understand why the needles need to be so much
    richer than the stock spec to make this car run properly!
    Does anyone have any ideas or experience with this exact model?

    Greg Solow
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    edwardbarnard at prodigy.net
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