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Model B

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Zenith Carburetor Float Mass and Performance Details

This page details the float masses of the three original style B-9550 Model B Zenith carburetor floats.

The 1932 Model B first used a cylindrical drum shaped float, then a rounded shaped float, and later released a rectangular shaped float on April 10, 1934.

The rectangular float style Model B Zenith carburetor is the most common version found today.

The pic above somewhat shows the relative differences between the early cylindrical drum float on the left, the subsequent lighter rounded float in the middle, and the final rectangular float on the right.

Discrepancies in proper float mass may lead to valve seating issues due to the inverted needle valve. This could then affect fuel level in the bowl and fuel consumption and carburetor performance.

Shown in the table below are the results of measurements using a digital gram scale on a sample of original B-9550 floats, including NOS and undamaged and unmolested nice used floats in my collection.

Model B Zenith Fuel Level:
The fuel level (not the float height) in the 1932-34 Model B Zenith carburetor float bowl was originally designed at 5/8" ± 1/32" below the fuel bowl gasket surface, per 1932 Ford Service Bulletins page 9, and 1934 Ford Service Bulletins page 227.

Use an external visible sight gauge mounted to the drain plug hole to measure the fuel level in the float bowl of an installed carburetor. Use fuel or mineral spirits, not water, to measure the fuel level (at the bottom of the meniscus). Vary the thickness of the fuel valve gaskets to change the float height and fuel level. Do not bend the float in any way.

It should also be noted that the carburetor itself is horizontal in the vehicle-installed position, even though the engine is inclined at 3.25 degrees to horizontal. The intake manifold flange is opposite-angled 3.25 degrees to produce the horizontal mounting condition when the carburetor is installed on the engine.
Each of the three float styles also used corresponding different upper casting assemblies, having different float hinge pivot brackets, and having different travel-stop features.





Additionally, the cast iron lower casting was different between the three float styles.

The cylindrical drum float design was used with a cast iron lower casting which had a 'plain' float bowl with no internal shelf feature on the outboard side of the bowl wall.

When the transition was made to the rounded float, the float bowl in the cast iron lower casting was revised and had an added horizontal shelf having a wide notched shelf in the outboard side of the bowl wall.

In the final lower casting design used with the rectangular float, the float bowl had a narrow straight shelf on the outboard side of the bowl wall.


Model B Zenith Rounded Float B-9950

Model B Zenith
Rounded Float B-9950
(Zenith 33014B)		 Mass
(grams)
B-9950 Drawing 11-13-31
Rounded, undamaged used 17.7
Rounded, NOS 1 18.1
Rounded, NOS 2 18.1
Rounded, undamaged used 18.3
Rounded, undamaged used 18.4
Rounded, undamaged used 18.5
Rounded, undamaged used 18.5
Rounded, undamaged used 18.8
Rounded, NOS 3 19.0

Model B Zenith Cylindrical Drum Float B-9950-A

Model B Zenith
Cylindrical Drum Float B-9950-A		 Mass
(grams)
B-9950-A Drawing 6-6-32 24.75 - 26.75
Cylindrical, NOS 1
Cylindrical, undamaged used 25.6
Cylindrical, undamaged used 25.6
Cylindrical, undamaged used 25.9
Cylindrical, undamaged used 26.4

Model B Zenith Rectangular Float B-9550-B

Model B Zenith
Rectangular Float B-9550-B
(Zenith 32121) 12-26-33, 3-20-34		 Mass
(grams)
B-9950-B Drawing 4-10-34
Rectangular, undamaged used 13.3
Rectangular, NOS 1 13.4
Rectangular, undamaged used 13.6
Rectangular, undamaged used 13.6
Rectangular, NOS 3 13.6
Rectangular, NOS 2 13.8
Rectangular, undamaged used 14.0
Rectangular, undamaged used 14.0
Rectangular, undamaged used 14.1
Rectangular, undamaged used 14.2
Rectangular, undamaged used 14.6

More related information on Ford Garage:

  1. For more Model A & B related information, use the Site Search box at the top or bottom of this page.
  2. Model B & 46 Zenith Carburetor Upper Casting Variations
  3. Model A Zenith Carburetor Float Mass and Performance Details
  4. Model A & B Zenith Carburetor Jet Sizes & Flow Rates
  5. Model B & 46 Zenith Carburetor Parts Catalog Illustrations
  6. Model B & 46 Zenith Carburetor Assembly Drawings
  7. Model B & 46 Zenith Float Valve Orifice Details
  8. Model B & 46 Zenith Carburetor Power Jet Circuit
  9. Model B & 46 Zenith Carburetor Power Jet Tube
  10. Model B & 46 Zenith Carburetor Power Jet Tube Instructions
  11. Model B & 46 Zenith Carburetor Catalog Data
  12. Model B & 46 NOS Zenith Carburetor

December 2015