QCMAC - Reassembly of Model A Zenith Carburetor

[@JWilliams81]

Thanks for posting up the video! Keep them coming.

[@rogerclark3162]

Sofield I noticed a few mistakes in the reassembly. Number one, back off the throttle idle screw first. Next insert the throttle shaft and plate. Tighten throttle shaft screw just enough that you feel the plate move plus one additional screw turn. Install the air adjustment screw 1-1/2 turns open.. Make sure the screw doesn't bottom. Install the float valve and washer and inlet screen, washer and plug. Turn top half upside down and set float 5/8 inch from float seam to bottom of top half. Install idle jet (no washer) and set aside. Bottom half. Install secondary well, cap jet, comp jet and main jet in bottom of carb base, don't forget the washers, then the drain plug with washer. Install AVR jet if it has one with washer. Follow with AVR housing. Wrap 2-3 turns of plumbers Teflon tape around threads first. Before installing back off driver housing screw 3-4 turns. Install choke shaft and plate. Install AVR driver and link between driver and choke shaft. Make sure choke link won't slip off driver when you work the choke. For overall best results use flow tested jets.

[@acmekanik9135]

Do you know of a zenith 1 lower casting that has a channel about 3/8"-7/16" wide machined across the secondary well connecting the bowl and throat together? I havent been able to find any pics of a casting like that. Only ones I see is like yours where the casting is completely flat over all three openings.

[@davidrenner9838]

This is a pressure balancing circuit, your factory float bowl vent should be plugged up with a pipe plug also. ALL carburetors that use an air cleaner from the factory have a pressure balancing circuit in them. I would bet that I did that modification to your carburetor. I can modify all Ford released model A & B carburetors so that you can run an air cleaner with out negatively affecting air fuel ratios as the filter gets dirty. In 1937 Zenith released a document telling Model A and B Ford owners to not use air cleaners because they’re Carburetors were not designed for them. This is not an opinion it is 100% a fact…. Carburetor design 101.