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basic physics

Air traveling thru a ventury has to increase in speed and the pressure decreases..PVT = a constant. change one and the others balance. A teter totter effect if one goes up the other has to go down. with the lower pressure in the Venturi it creats a "suction" It sucks the fuel into the Carb. With A lower fuel level It would require more suction to lift the fuel. With a constant flow of air it will not suck as much fuel per the amont of air. With a higher fuel level the it can suck in more fuel for the same volume of air.
 

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It all depends on what carb your talking about. I've experimented with Q-jets and found that too high a float setting just wastes gas (water over the dam). I lowered the the float level until it bogged or basically ran out of gas. Then I raised the float an 1/8". This turned out to be the best setting for mileage and performance. I think too many people lose to much sleep over float setting heights. More important is that the float does float and not soak up fuel and sink. I use a general rule of thumb on almost all carbs to set the float so it is level when the needle and seat are closed.
 

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bentwings
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There is a certain range that each carb will work at. However if you tilt the carb as in off road or cause the fuel to slosh due to acceleration of deceleration the level changes. The carb then either goes lean or rich depending just where the fuel in the carb is in relation to the venturi or venturies if you have multi carbs.

My motor sits at a an angle with the rear down....a little more than usual. also the carbs are mounted side ways. This causes less problems on accel and decel however going around corners is a different matter. At first the motor would go very rich or very lean depending on corner direction when the carbs were set to the bottom of the sight hole.

Fortunately I have an AFR gage and could see this very quickly. I just set the floats a bit lower untill I can corner as fast as I feel is necessary. My car is not a road racer but I do like to keep up with traffic in the intersections and freeway ramps.

I just re jet a little to make up for the loss of float height. Works for me.

The carb mfg spend a lot of time getting a good float height for the attitude of the carb. But when we deviate from this we are on our own.

Race car guys do all sorts of things to maintain fuel in the bowl at a consistant height. Drag racers go after accel and decel and circle track guys look for what happens in corners. Us street guys just have to mix all together and come up with what works.
 
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