aav-26 stuck vacuum piston

[mr41cadillac]

in rebuilding  my aav-26 Stromberg carb. so far heres what we have found. 1. the vacuum piston was stuck 2. one gasket broken.3 some internal parts need cleaning.  question is would the stuck pump cause to0 much gas entering engine resulting in all the carbon ? ? thanks john

[Steve Passmore]

What do you mean by Vacuum pump John? The vacuum for the distributor is taken directly from the venturi, no pump.   If you talking about the accelerator pump that's pressure and connected to an arm that's connected directly to your throttle linkage and cannot stick. If your talking about the non return valve in the bottom of the accelerator chamber? that could stick. Some pictures would help.

[mr41cadillac]

steve it I s called the vacuum piston. . I have an old motors manual and they have a picture. looks like a small metal piston with a long spring. it screw in to the upper part of carb . the piston goes up and down in upper par t , it was stuck. the picture is in an old motors manual from late 40s or early 50s. its not the accelerator pump with the leather piston.  john

[tturley]

Is that the piston that controls the metering rods?

[Steve Passmore]

The piston your referring to is all to do with the automatic choke.  When you get into the car from cold and press the accelerator once, the choke butterfly will close to give maximum gas for starting. As soon as the engine is running it cannot keep running with the butterfly completely shut so vacuum from the venturi opens the butterfly a very small amount to allow the engine to keep breathing until heat from the manifold stove opens it completely. If this were stuck and the butterfly was fully shut then yes, the engine would flood but this would have been fairly obvious to you before now that the choke was not opening surly??