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Old 01-09-2013, 12:09 PM   #1
TDO
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Default Model B Zenith Carburetor

I have A model B zenith carburetor. I was thinking about putting it on my 1930 Model A . Is there any advantage using the Model B Zenith over the Model A zenith Carburetor.
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Old 01-09-2013, 12:21 PM   #2
BRENT in 10-uh-C
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Default Re: Model B Zenith Carburetor

Well, ...Yes, -and No.

If you compare the two carburetors themselves you will see the Model-B has a larger venturi and throat which "should" allow more cfm of fuel and air. The "should" comes in that you will find the stock Model-A intake has a 1.00" rough cast draw tube. A Model-B intake has a 1.250" diameter draw tube meaing it will flow about 30+% more air. I realize someone is going to say well it is only " larger in diameter however the airflow goes up on the square when the diameter is increased, and the bore surface of the B intake is different too.

I would suggest that you consider opening up your stock A intake and port match to the B carburetor, or install a Model B intake. The downside to the B manifold is the mounting flange on the B manifold is slightly canted requiring a little alteration to be able to connect the choke rod to the B carburetor. Hope this helps.
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Old 01-09-2013, 01:18 PM   #3
ctlikon0712
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Default Re: Model B Zenith Carburetor

In addition to what Brent said, the model B float is on a different pivot axis so that on sudden stops the needle and seat won't unseat and thus less possibility of causing a stall.
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Old 01-09-2013, 02:24 PM   #4
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Default Re: Model B Zenith Carburetor

Don't forget the power tube that the B carb has. Actts like an accelerator pump. Read up on it on Vince's site:

http://www.fordgarage.com/pages/bpowertube.htm

Over several decades I have tried Tillotson's, Simmons, Allstate, and lots of Zeniths but I have been using a Zenith B carb on my Tudor driver for a couple of seasons now and may not ever go back to my old stock Zenith. It is running on a stock A manifold. Plugs burn nice an tan. My perception of it is that I need fewer downshifts for going uphill. Easy steady top end power. You can also run with the GAV completely closed. This is the carb to use if you ever go to a dual updraft manifold.

Please do a search on Ford Barn of previous threads on B carbs. Lots of pros and cons already discussed on FB so it goes back to different strokes for different folks.
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Old 01-09-2013, 04:12 PM   #5
Purdy Swoft
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Default Re: Model B Zenith Carburetor

I agree with everything said.If you've got the style that was used with the B engine. There was a service replacement B carb that was sold as the first replacement for the Zenith one two and three carbs, this carb had a smaller inside diameter venturi. The larger B venturi will interchange. The B intake has larger passages and I think that the flat top of the B intake may have been for better flow and distribution to the cylinders.The Swan design intake manifolds were flat across the length. Here is a picture of the intake and dual B carb set up on our speedster. The name on the intake is UNI-FLO but it looks like the swan design. It was made in the thirties for the B engine. It has large ports and runners and way out performs the Trojan dual up draft manifold and B carbs on our roadster.
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Old 01-09-2013, 07:53 PM   #6
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Default Re: Model B Zenith Carburetor

At the Boise meet last summer they had a seminar on Model A eng. mods & performance with dyno. results. I was surprised to learn that a stock Model A motor had less power output with a "B" carb. then it did with a stock Model "A" carb. On the other hand I have a "B" motor in my 68C Cabriolet & have an "A" side bowl carb on it & it runs great.
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Old 01-09-2013, 10:20 PM   #7
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Default Re: Model B Zenith Carburetor

Both my B engines use the stock A manifold & have lots of power-enough that I wont bother to have the manifold bored out.
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