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Technical Zenith carburetor float settings

Discussion in 'The Hokey Ass Message Board' started by carbking, Oct 11, 2021.

  1. carbking
    Joined: Dec 20, 2008
    Posts: 3,161

    carbking
    Member

    As a general rule on newer carburetors, for setting Zenith carburetor floats, Zenith's suggestion was that if a new float and new fuel valve were used, the float would be correctly set.

    However, in 1957, Zenith did publish a guide for VISUAL CHECK ONLY for floats on older carburetors. Here is that list:

    https://www.thecarburetorshop.com/Zenith_float_settings.jpg

    Remember, NEVER bend a Zenith float for adjustment. If the dimension is incorrect, then adjust by changing the thickness of the float valve seat gasket.

    Jon.
     
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  2. bobbytnm
    Joined: Dec 16, 2008
    Posts: 1,443

    bobbytnm
    Member

    Great info!

    Thanks
     
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  3. Truck64
    Joined: Oct 18, 2015
    Posts: 5,095

    Truck64
    Member
    from Ioway

    "The Charts Shown Are To Be Used For Visual Check Of Fuel Level Only"

    So ... what does that mean, exactly? Thanks Jon! @carbking
     
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  4. carbking
    Joined: Dec 20, 2008
    Posts: 3,161

    carbking
    Member

    This was a visual check BEFORE reassembling the carburetor. The actual adjustment for each carburetor was accomplished by using a regulated fuel pressure system, and setting the FUEL level (not the float level) at the specified pressure.

    This generally was accomplished with the use of a special tool (which can be made if the mechanic does not have one).

    https://www.thecarburetorshop.com/Glass_float_tool_1.jpg

    https://www.thecarburetorshop.com/Glass_float_tool_2.jpg

    The tool came with a number of different threaded adapters, to screw into the carburetor bowl drain hole after the plug was removed. As the glass tube in the tool is open at the top, the fuel level in the bowl will be duplicated in the glass tube, therefore may be measured.

    The proper pressure from the fuel pump, the proper orifice in the float valve seat, and the proper float adjustment can make a huge difference in fuel economy, AND performance.

    Jon.
     
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  5. Truck64
    Joined: Oct 18, 2015
    Posts: 5,095

    Truck64
    Member
    from Ioway

    Well ... OK. I sort of understand what they are getting at, it's the fuel level in the bowl that counts, a lot of people don't get that. TheY set the float height on the bench and think that's the end of it. It's interesting how different manufacturers tried to accomplish this. I read some carb guy say once, maybe it was you I dunno, if he could only make one (1) carb adjustment, the fuel height would be it.

    Btw, how did Zenith carburetor people not get zapped by Zenith radio people for copyright infringement anyway? Or the other way around, depending who was first. Zenith radio was incorporated in 1923
     
  6. Glenn Thoreson
    Joined: Aug 13, 2010
    Posts: 265

    Glenn Thoreson
    Member
    from SW Wyoming

    What model is your carb. Zenith made a lot of different models. What car do you have?
     
  7. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 9,474

    Johnny Gee
    Member
    from Downey, Ca

    Carb came first. The french definition for zénith isn't the same as the english definition for zenith. Beside's both products are so dissimilar.
     
  8. carbking
    Joined: Dec 20, 2008
    Posts: 3,161

    carbking
    Member

    The Zenith carburetor was invented in 1903 by a French engineer by the name of Bavery, and a company formed in Lyon.

    The Zenith was superior to other period carburetors (Stromberg did not come along until maybe 1909), and satelite Divisions of Zenith quickly appeared in other countries.

    Zenith U.S.A. fairly quickly became the largest of the Zenith companies.

    Some of these companies had either a working relationship (or maybe just worked under the table). I have no desire to study corporate alliances, nor do I have the time. But as an example, the Zenith two-barrel (Zenith-UK) used on the R-R Phantom III was a Stromberg design, modified by Zenith UK for an auto choke among other mods. Delahaye and Desloge also used Stromberg designs with different linkages, and metric rather than S.A.E. fittings.

    As to setting the fuel level, it was much more critical on updraft carburetors than downdraft. Typically (and a rule of thumb we used on carbs for which we had no data) the fuel level on an updraft was set 1/8 inch below the discharge orifice of the main discharge nozzle. If the fuel level was too high, fuel would leak from the discharge nozzle when the vehicle was parked on a steep hill. If the fuel level was too low, the engine would have starting issues (remember that with an updraft, fuel must be pulled UPWARDS from the carburetor to the intake manifold.

    For those that would like to experiment with checking fuel level in this manner; but do not wish to invest in an expensive antique carburetor tool:

    Visit your FLAPS, and acquire a brass fitting that will screw into the bowl drain (assuming your carburetor has one, if not, probably not going to use this tool), an ell fitting to attach to the first, a short length of metal tubing, another ell fitting, a straight fitting with a hose barb, and maybe 8 inches of clear plastic hose. Put it all together like the picture, and you have an inexpensive fuel level gauge.

    Jon.
     
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  9. Truck64
    Joined: Oct 18, 2015
    Posts: 5,095

    Truck64
    Member
    from Ioway

    I mean the name "Zenith". Can't even call the Super Bowl the Super Bowl anymore without paying tribute. Gotta call it the "Big Game" or somesuch. See where I'm goin' with that?

    Sorry for getting off topic. Kind of a rarity with me.
     
  10. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 9,474

    Johnny Gee
    Member
    from Downey, Ca

    I did refer to the names of both the carb and radio/tv.
     

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