On Mon, 05 Dec 2005 19:34:20 GMT, Michelle P
wrote:

Roy,
It may be a clever girl who enlightens you.
This has puzzled me. I am a Fuel Injection person (Jet engines, IO-540s
and the like).
He had an interesting thought based on his empirical data. The float is
the problem. It is riding too low in the bowl thereby allowing the level
of fuel to be a little too high. When the throttle is closed there is a
momentary lower pressure in the throat of the carb and sucking excess
fuel. Depending on how rich the charge is it may cause it ti stumble.
I was just looking into my Powerplant textbook. There is an Economizer
system that adjusts the mixture based on the throttle setting. Richer
for max power and leaner for cruise. If this is set up wrong it could
stumbler.

One minor point, on a basic MS carb the "economizer" circuit is
essentially a calibrated vacuum leak into the fuel delivery stream. At
higher MAP/ambient differential it leaks more air, lower differential
it leaks less. If you have an economizer circuit, it is adjusted
according to the spec # of the carb, and can be closed off completely.
It is a "fixed" circuit, and does not vary mechanically with throttle
position.

FWIW, have seen a bunch of stumbling O-360's, but have never been in a
320 that had the problem.

Regards;

TC


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