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The carb on my 1929 640 runs too rich. The float is set right and the air valve is set to factory measurements. Runs rich at idle and loads up. Sooty exhaust.

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Take the float out and put in warm water hold it under the water and look for bubbles. I have had several of the floats leak

float is good, no leaks

Float valve not properly sealing?

Brand new needle and seat.

Is the car still using the vacuum tank? If not, is the new needle and seat calibrated to handle higher pressure than gravity feed?

There is supposed to be a bleed passage that pulls fuel above the throttle plate at idle the same way as idle air bleeds on a downdraft carburetor. If that is clogged the motor will load during idle.

Tim

Still using the vacuum tank, which works well. I have heard about the bleed passage, but have never been able to identify where it is in the carb. Are you talking about the carb pictured in the first post above or the later carb?

Jim,

According to Dykes Manual, rough idling and loading up at low throttle can be caused by an air leak or a plugging of the suction tube that goes from the bottom of the carburetor to the intake manifold. The remedy is to clean it and its connections and reinstall. Hope this helps.

Phil

Here is a quick check to see if the spring setting on the air valve is correct. If the valve is pressed down slightly to open it, does the engine run rougher. Then push the valve closed by pressing on the end of the stem that is in the air intake above the choke butterfly. The engine should also run a bit rougher. If one way improves the running the air valve spring adjustment may need to be moved to either increase or decrease the tension.