31-05-2021, 08:19 AM
Hi
Here's some data I have noted down for the standard Zenith 26VA for the Austin 7. The body should be stamped CS548 (Contract Sheet 548), and there should be an identity mark 7 (Not a 10) cast into the flange.
Choke tube diameter 17 mm
Main Jet 57 (Smaller Brass Jet in bottom of float chamber)
Compensating Jet 50 (Larger Brass Jet in bottom of float chamber)
Slow Running Jet 60 (Tiny brass jet near top surface of bowl)
Progression Jet 100 (Hidden under a screwed inspection plug on underside of main body, near throttle plate)
The idling circuit is as follows: Fuel passes through the idling jet, and has air mixed with it through a small hole. Additional air is mixed in via the tapered air bleed screw (Idle mixture adjustment). The mixture then passes down internal drillings and out of the idling hole just downstream of the throttle plate. There is a parallel circuit through the Progression jet which exits just next to the throttle plate, and is supposed to prevent a flat spot as the throttle just opens.
I presume you are priming the carb using the lever on the fuel pump ? If so, the needle valve ought to stop flow well before the point where fuel seeps from the bowl to body seam. I don't know the spec for the fuel height, but would guess at 5 or 6 mm below the seam. Once cut off, the priming lever will offer less resistance and sounds of fuel flow should stop. The fuel level should settle at something like 1 or 2 mm below the point where it can pass out of the nozzle into the venturi, so that fuel is only siphoned out and introduced once airflow into the engine starts.
Here's some data I have noted down for the standard Zenith 26VA for the Austin 7. The body should be stamped CS548 (Contract Sheet 548), and there should be an identity mark 7 (Not a 10) cast into the flange.
Choke tube diameter 17 mm
Main Jet 57 (Smaller Brass Jet in bottom of float chamber)
Compensating Jet 50 (Larger Brass Jet in bottom of float chamber)
Slow Running Jet 60 (Tiny brass jet near top surface of bowl)
Progression Jet 100 (Hidden under a screwed inspection plug on underside of main body, near throttle plate)
The idling circuit is as follows: Fuel passes through the idling jet, and has air mixed with it through a small hole. Additional air is mixed in via the tapered air bleed screw (Idle mixture adjustment). The mixture then passes down internal drillings and out of the idling hole just downstream of the throttle plate. There is a parallel circuit through the Progression jet which exits just next to the throttle plate, and is supposed to prevent a flat spot as the throttle just opens.
I presume you are priming the carb using the lever on the fuel pump ? If so, the needle valve ought to stop flow well before the point where fuel seeps from the bowl to body seam. I don't know the spec for the fuel height, but would guess at 5 or 6 mm below the seam. Once cut off, the priming lever will offer less resistance and sounds of fuel flow should stop. The fuel level should settle at something like 1 or 2 mm below the point where it can pass out of the nozzle into the venturi, so that fuel is only siphoned out and introduced once airflow into the engine starts.