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Model A & B

Ford Garage

Cylinder Head Identification

Model A Head

The North American Model A Ford was built from 1928 to 1931 primarily with a single cylinder head design.

Pictured below is part number A-6050-A. This is the standard cast iron 4.22:1 compression ratio Model A engine cylinder head. This head uses 7/8-18 inch size spark plugs.

It has the four-stud water pump attachment design, and the separate water outlet on top of the head.

The original Model A cylinder head had no significant external markings. Later replacement heads made after 1931 frequently had the Ford script or Ford USA marked on top between the distributor hole and the head stud. Many also had casting dates and other assorted numbers, markings, and codes cast onto the surface.

Pictured above is a view of the standard Model A cylinder head with the 4.22:1 combustion chamber design.

Compare this pic to the 'Police' head and Model B head combustion chamber designs shown below.

Note that this head also has the oblong elongated hole in the center of the head which was added in September 1929. The oblong hole was also added to the small-bore Model AF head, and to both Model A and AF cylinder head gaskets at that same time (EI 13911).

Ford indicated that the oblong hole was added to improve water circulation, but it is likely that the primary purpose was to provide better core support and registration in the mold, and reduce core shift which caused scrap heads during both casting and subsequent machining operations.

Using a Model B head gasket with a Model A head is not advised.
The Model B head gasket profile is different than the Model A head, and the edge of the gasket can overhang into the combustion chamber around the valve pockets.

If the edge of the gasket and fire ring overhangs into the combustion chamber, the edge of the gasket can be burned. This will not cause a water or combustion leak at this point, but should be avoided.

The Victor 800C illustrated below is one of the correct original Model A head gaskets.


Model A Police Head

In 1931, Ford introduced the A-6050-B cast iron high compression head (marked 'B'), often referred to as the 'Police' head. The compression ratio of the 'Police' head was 5.22:1, compared to the standard Model A head at 4.22:1. This head has a so-called heart-shaped combustion chamber design.

The Police head also uses the standard four-stud water pump, has the separate water outlet on top of the head, and uses 7/8-18 inch size spark plugs.

Thanks to Craig Lewis of British Columbia, Canada for providing the great photos below of his original 'Police' head shown here on Ford Garage.

Photo courtesy of Craig Lewis

The 'Police' head has a large letter "B" (the part number suffix) cast in the top surface near the number two spark plug to easily identify it. The "B" does not signify a Model B head. It is the suffix of the base head part number.

Photo courtesy of Craig Lewis

Pictured above is the combustion chamber of the A-6050-B 'Police' head.

This 'Police' head uses a different gasket than the standard Model A. Each gasket is designed to fit its respective combustion chamber.

Pictured below is the head gasket for the A-6050-B 'Police' head.

The head gasket is designed based on the cylinder head, not the block. The gasket must fit the edge of the combustion chamber to seal properly and not expose the gasket to hot combustion gases. Using the wrong gasket on a head can lead to early burn-out or blow-out of the gasket.


Model A Small Bore Head

Ford also produced an AF-6050 head for use with the smaller bore Model AF engine produced for Great Britain.

Pictured below is the head gasket for the AF-6050 small bore (3.030 inch) head.


Model B Head

In 1932, Ford introduced the B-6050 cast iron cylinder head (marked 'C') pictured below. It is the standard 1932-34 Model B head having a 4.6:1 compression ratio. The B-6050 is the only cylinder head originally used on the 1932-34 four cylinder Model B engines.

The compression ratio is higher than that of a standard Model A cylinder head, yet it is less than the compression ratio of the Model A 'Police' head (marked 'B'). The Model B cylinder head also uses 7/8-18 inch size spark plugs.

As seen in the pic above, the Model B head had a large letter "C" cast in the top surface to aid dealer parts counter men in easily distinguishing it from other earlier heads. The "C" signifies a Model B head, not a so-called "Model C". In this case, the "C" is not related to the actual part number prefix or suffix.

In the early 1930s, Ford was experiencing a proliferation of differing parts in their business systems, partly due to the addition of the Model B and the Model 18 flathead V8 models, as well as the proliferation of AA and BB truck models. Ford flirted with a changing variety of ways in which the part number prefixes and suffixes were assigned for identification during that time.

The Model B head is easily identified by the three-bolt water pump attachment. The three-bolt water pump has an integral water outlet as part of the pump casting. There is no separate water outlet mounted to the head.

The change of the water outlet from a separate part on a Model A to an integral part of the water pump casting on the Model B allowed Ford to gain a cost savings, use 14 identical head studs, and to get a more consistent torque and head gasket seal. This was a big improvement for the Model B over the Model A.

Pictured above is a view of the standard Model B cylinder head having the 4.6:1 ratio combustion chamber design. This is the so-called heart-shaped combustion chamber.

Also seen on the Model B head above are the two 1/4 inch diameter "steam holes" on either side of the center head stud. These holes are quite near the edge of the Model B gasket and are often difficult to seal against water. These holes align to matching holes in the Model B head gasket and in the Model B block.

The use of a Model A head gasket with a Model B head or Model B block is not advised.
The Model A head gasket profile is different than both the Model B head and Model B block, and the edge of the gasket is even closer to the two center "steam holes" in the head (and block) than that of the correct stock B head gasket.

If the Model A head gasket does not seal the Model B steam holes properly, water can be pulled into the cylinder on the intake stroke causing water loss.

Conversely, on the exhaust stroke the piston can push exhaust into the cooling water and cause foaming visible in the radiator and overheating.

The Victor 900 shown below is one of the correct original Model B head gaskets.


Foreign Cylinder Heads

In later years Ford-Köln in Germany produced a cast iron 7.0:1 higher compression ratio version head BG-6050-B, as well as a cast iron 8.5:1 head numbered G28TG-6050 which were both specified for wood gas compressor engine use. The 7:1 head uses 7/8-18 inch spark plugs, while the 8.5:1 head uses 14mm metric spark plugs.

There are also Ford-Köln cast iron Model B heads marked G98T-6050 and G38T-6050 with the three bolt water pump provision, which have a standard Model B combustion chamber design of 4.6:1 compression ratio, but use 14mm metric spark plugs.

In addition, GAZ in Russia produced the M-6050 cast iron Model B style 4.6:1 ratio combustion chamber cylinder head (using 18mm metric spark plugs) in the Soviet Union from the 1930's to 1940's. See related links below.

Ford England also produced a BF-6050 cast iron head for use with the small displacement 3 inch bore Model BF engine produced in Great Britain in the early and mid 1930's.

The BF prefix cylinder block has smaller cylinders, a different valve layout pattern, and different water jacket. The BF prefix cylinder head has a matching combustion chamber and water jacket, and will not fit on a Model A, AF, or B block. The BF head will only fit a Model BF block, and uses a unique BF head gasket.


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 A & B Cylinder Head Compression Ratios
  3. Model B Simmons High Compression Cylinder Head
  4. Model B Russian GAZ Cylinder Head  
  5. Model B Brumfield Cylinder Head and Gaskets
  6. Model A & B Cylinder Head Gasket Guide comprehensive listing
  7. Model A & B Model C Myth and Terminology
  8. Model A & B Cylinder Head Nut Tightening Sequence
  9. Model A & B Cylinder Head Gasket Installation Instructions by Larry Brumfield
  10. Model A & B Snap-on Cylinder Head Nut Wrench proper torque application tool
  11. Model A & B Cylinder Head Flatness Requirements by Larry Brumfield
  12. Model A & B Cylinder Head and Distributor Pullers by Ron Cloat
  13. Model A & B Broken Cylinder Head Stud and Bolt Removal
  14. Model A & B Cylinder Head Stud Removal Tools

October 2002