Flooding of the Zenith Carburetor

[mbailout2]

I decided to take the Weber carb off Molly and try a Model B Zenith Carb. She ran really well with the B carb, but when I braked for a stop, the carb flooded out. I have the "How to restore your Model A, Volume 7" that has a chapter on the Zenith Carb and a chapter on the leaking issue. The leaking wasn't a big deal as it seems if the primary jet was lower than the cap jet in the venturi, it would allow gasoline to bleed out of the bowl. It should be at least 1/8 inch higher than the cap jet. It also mentioned that the flooding is inherent with this carburetor, for if the fuel level was level in the fuel bowl, braking would cause the gasoline to push back and then come forward as a wave higher than the primary and cap fuel jets and would flood the carburetor. The only solution that I can see is to set the float level to shut off the fuel to the bowl so it is at a lower level. This might help on slow breaking, but I'm not sure about breaking in traffic, as starting a flooded engine takes a little time. I've been through this.
Also, I'm not sure there would be sufficient fuel to come to a higher speed again without backfiring, as the engine would be running lean looking for more fuel.

Anyone else having this problem? Anbody find a solution for this inherent problem other than designing some sort of baffle in the fuel bowl?

Mark
Molly with her B Carb:

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[Drew Mashburn]

Mark:

Per chance, do you eat off that engine? Clean! Nice!

Happy "Thanksgiving"!
-- Drew

[mbailout2]

Thanks Drew, back at ya: Happy Thanksgiving.

I keep Molly pretty clean for the Shows, which means top, bottom and inside. People at the shows think I trailer her, but I drive her to every show in the area to a radius of 60 miles and travel off the main highways.

Mark

[mbailout2]

Figured out that adjusting the float in the fuel bowl to keep the gas level down seemed to stop the flooding when stopping. It doesn’t have an adjustment tab so I bent the hinge plate so the float is angled down now at about 15 degrees, and the bowl now fills to about a little less than 1/2.
I visited a friend that has a 32BB to check his carb setup, but he was away, and the carb was missing from the engine. I saw the fuel pump setup and I figured the lack of a pump might be my problem in getting a proper idle on Molly. The static pressure from the B fuel pump is 1 ½ to 3 PSI.
I connected my inline pump with a regulator set at 3 PSI to my B carb, but the results didn’t change and I still was not happy with starting and the idling of Molly’s engine.
The whole thing about the B carb was an experiment for me to see how Molly would run with a Zenith carburetor. I was able to see that she ran better with the Weber carb setup, so I put the Weber back on Molly.

Molly with her Weber

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[vtwinsideways]

Gravity provides plenty of flow for all but "crazy racing" mode with the B carb. The pumps were for the rear mounted (below the carb) tank set-ups on Model B's. By chance do you have the round barrel style early float in your B carb? This can cause some slosh problems at stops. Usually there will be no problems when you take off, only when you stop. The second and third versions changed the float shape and added a baffle and spring assist. B carbs can be a great addition to an A/AA motor, I saw great results adding one to mine, but I have the early style float and she stalls at the first few stops of a trip if I'm not careful. A few pieces of info I might suggest are: "Restoring the Model A and B Carburetors- The Rex Rehis Way" By Gordon Biggar, the website http://www.fordgarage.com/ has a font of useful B carb info and the handy little insert that comes with a Model B carb rebuild kit is insightful as well, providing some great little tips for setting your B carb as there are subtle differences in the A and B set-up that Rex doesn't cover quite as clearly. I will tell you that you will not get better performance out of a B than you do from a properly maintained Weber. Luke

[vtwinsideways]

I almost forgot, these are a great "must have" when setting a B carb:

The only place I can find them in stock is Mike's. Part Code: B9599
Price:$9.00 Luke

[mbailout2]

Thanks for the info Luke. I have the later model B Carb version that has a slab type float with spring assist and baffle, although I think the baffle is facing the wrong way to prevent any “sloshing”. Bending the float down about 15-20 degrees seemed to help the flooding when stopping. Molly ran well with the B carb and I was surprised at the acceleration, but I wasn’t satisfied with the “starting and idling” of Molly. With the B Carb, Molly idles like an old Model A! I will definitely check out your references for the B Carb for future use.

Your right, the Weber is definitely a better performer than the B Carb, but I wanted to see how Molly would run with it. With the Weber and electronic ignition, Molly starts with one hit from the starter. I don’t have the throttle hooked up to the steering column control, so with the B Carb, I was starting Molly with my toe on the starter and my heel on the accelerator. At my age that was fun!! I’ll be walking with a limp for awhile!!

I did a lot of work on the Weber, jetting and re-jetting trying several various sizes between 120-135mm, but it worked the best with the original primary jet of 140mm. The secondary I changed from 135mm to 125mm. I believe the main jet on the zenith 1 is .97mm if you convert it from the drill size. I’ve got a conversion chart around here somewhere. Anyway, I’ve had that Weber apart (and Zenith) so many times I could do it with my eyes closed. The hardest part is remembering!!

My next project with Molly is pulling her rear end and getting the “slack” out of it. I need to get it done before January as the Show circuit begins then. I had a ride in “Otis” this past weekend, which was the first time I rode in another AA. Otis seemed to have a “tight butt” so I see I have some work to do on Molly.

My Zenith B Carb and manifold is available to someone that could use it. When I purchased the B Carb last month, I was told it was rebuilt, and it appeared so with a visual inspection, and the throttle and choke are tight, and….it doesn’t leak.

Mark

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[vtwinsideways]

I'm interested, what do you need for it? Luke

[the99car]

Checkin' out my AA's rearend were ya - Kenny