Berry and Jim---Yes, if a needle and/or jet develops a flat side from
rubbing on each other, it will permit more fuel to flow from the jet,
past the needle. I would think that it would take a lot of miles to
accumulate the kind of wear to cause a "flat," since both components are
lubed in fuel at all times. Still, there is a way to at least measure
the possible flat side on the needle. All that is required is a good one
inch mic with a small, flat spindle and anvil. By carefully measuring
the non-rubbing side and comparing it to the side that rubs the jet, one
could get a comparison. I would have to be done at precisely the same
place on the needle taper, given that they get a couple of thousandths
smaller, by design, as they narrow down towards the bottom end. Anything
that has a flat of .001 or more will let more fuel flow at that
particular throttle setting.
Measuring the out-of-round at the jet would be more difficult to do, and
would require a dye, like ink, to be on the walls inside of the jet.
Rubbing the inside of this jet with a needle would cause the jets "ink"
to be rubbed off, except where it is worn, or flat. This would be right
at open top of the jet, where the widest part of the needle makes
contact.
While it won't give mileage comparable to the numbers posted in some of
todays messages, it's possible to pick up around a 5% improvement by
simply lowering each needle to make the annular opening smaller, thereby
leaning the mixture at idle, and thruout the rpm range. Most owners
won't do this, even in a gas crisis, as it usually will reduce
performance slghtly. Since I have an air/fuel monitor and 02 sensor, I
can tell quickly what each setting and "experimenting" does in regards
to mileage, and to some degree, perceived horsepower.
Now Berry, aren't you sorry you asked?
Dick Taylor
CF11143
L.A.
|