>The engine was from a 69 Spitfire MKIII. I dont think the carb and intake
are correct >because the 69 MKIII had dual carbs (?). I think I have one
of the non-adjustable >carbs. I have not touched the jet/needle in the
carb either. As far as adjusting the >mixture, do I simply use the idle
trimming screw on the side of the carb?
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The mixture is controlled SOLEY by the shape of the needle and its
relationship with respect to the jet orifice. What you do when adjusting
one is to move the needle up or down with relation to the jet bore -
slightly leaning or slightly richening the mixture. - the only thing the
"large idle trimming screw" (if this is what you are referring to and not
the idle speed set screw) will do is LEAN out the mixture. Basically it
was a compensation screw for when the motor became worn you could adjust it
slightly to compensate. These were really for emission use as you would
never notice the change unless hooked up to a co meter. - Truly non
adjustable carbs have no allen slot inside the bottom of the piston damper
bore (and the only way to tell is to look and see which is very hard to do
because its long and narrow, and should be full of oil) You can also tell
by removing the jet, and if its a non adjustable one it will have a large
diameter (about 1/4 inch x half an inch long) retainer with a spring
loaded, biased needle. That may be a way to tell also, for I believe that
only the non adjustable carbs had spring loaded biased needles, but it's
been so long since I looked I can't really remember. Some one else on the
list surely will though and will correct me if I'm wrong (please) - I don't
recall the spitfires ever using them - but I may be wrong as that would be
about the right year - 69-70 is when the GT6 used them - again, IF its the
right carb and needle then something else is leaning it out like a manifold
leak
Barry Schwartz - San Diego -(bschwart@pacbell.net)
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