Model A & B Style
Ford Garage
Cast Iron Cylinder Head Compression Ratios
A variety of cast iron cylinder heads and compression ratios have been made for the Model A and B (& G28T) style engines over the years by Ford globally, as well as by aftermarket producers.
The original Model A Ford compression ratio was 4.2 to 1, which is quite low by most standards. Other cars of that era typically had ratios in the 5-6 to 1 range. Since that time there have been numerous aftermarket heads made having increased compression ratios, more power, and better performance.
Higher compression ratios can also result in better cooling (compared to lower CR) despite higher combustion chamber pressures and temperatures at the same speeds and loads. Higher ratio heads tend to run cooler because more of the fuel energy is converted into power, and less into heat at those higher ratios.
Aluminum cylinder heads are not discussed here or elsewhere on Ford Garage. A cast iron head is recommended.
Summarized below is a list of cast iron cylinder heads and their combustion chamber shapes and compression ratios for a variety of original applications from 1928 through the mid 1950s, as well as a few more recent examples.
Heads highlighted below in green are the most useful heads to look for. Inspect carefully for cracks and damage at water openings, head stud holes, and in spark plug threads.
Model A Cast Iron Cylinder Heads:
(Four-stud Water Pump Provision)
| Ford Part Number |
Description | Combustion Chamber Shape |
Combustion Chamber Volume (cc) |
Published Compression Ratio |
|---|---|---|---|---|
| A-6050-A | Ford USA, Global 1928-31 Standard Production head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Also produced by Ford Canada, Ford England, and Ford Köln Germany |
Wedge | 242-248 | 4.2 :1 |
| A-6050-B | Ford USA 1931 Production High Compression "Police" head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked with a large "B" on top Buyer Beware: Prone to cracking. Inspect carefully. Can use a Model B head gasket on a Model A block. Requires a Model B head gasket on a Model B block. |
Heart | 178-184 | 5.2 :1 |
| AF-6050 | Ford Dagenham England, 14.9 HP (R.A.C.) 1928-31 Standard Production 3 inch bore head Model A, 4 stud water pump This head was produced by Ford England for the 2.2L 14.9 HP (R.A.C.) Model AF engine |
? | 144-150 | ? :1 |
| Part Number or Marking |
Description | Combustion Chamber Shape |
Combustion Chamber Volume (cc) |
Published Compression Ratio |
| MF 1 | 1930s aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked "MF 1", and "Made in USA" on top |
? | ? | ? |
| F1 MF | 1930s aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked "F1", "MF", and "Made in USA" on top Copy of Model A Ford combustion chamber |
Wedge | 242-248 | 4.2 :1 |
| A6050A | 1940s aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked "A6050A" and "Made in USA" on top Copy of standard production Model A Ford combustion chamber |
Wedge | 242-248 | 4.2 :1 |
| B6050 Speed Head (Variation 1) |
1930s aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked "B6050 Speed Head" on top Buyer Beware: Although marked "B6050 Speed Head" on top, this head is actually a total copy of a standard production Model A Ford (4.2) wedge combustion chamber and head, not a higher compression (5.2) A-6050-B nor a (4.6) B-6050 Ford head. Copy of standard production Model A Ford combustion chamber The Variation 2 of this head marked "B6050 Speed Head" has the Model A (5.2) "Police" combustion chamber, along with the Model A 4 stud water pump provisions |
Wedge | 242-248 | 4.2 :1 |
| Model A (Variation 1) |
1930s-40s aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked "Model A" on water hump in raised letters No other markings or date codes Copy of standard production Model A Ford combustion chamber Note that this head marked "Model A" also appears with 5.2 ratio heart combustion chamber |
Wedge | 242-248 | 4.2 :1 |
| Hoof | 1930s-40s aftermarket head Model A, 4 stud water pump Metric 18mm (?) spark plugs, over intake valves Marked "Hoof" on top Similar to standard production Model A Ford combustion chamber except for the additional frog shape like the underside of a horse's hoof Uses a Model A head gasket |
Hoof | ? | ? :1 |
| B6050 Speed Head (Variation 2) |
Early 1930s aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked "B6050 Speed Head" on top Buyer Be Aware: This head is a copy of the standard Model A Ford A-6050-B (5.2) combustion chamber, with the four-stud Model A water pump provisions. Copy of Model A Ford A-6050-B "Police" head Can use a Model B head gasket on a Model A block. Requires a Model B head gasket on a Model B block. |
Heart | 178-184 | 5.2 :1 |
| A6050B Speed Head |
Mid to late 1930s aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked "A6050B Speed Head" and may have "S-S" and/or casting date on top Copy of Model A Ford A-6050-B "Police" head Can use a Model A or B head gasket on a Model A block. Requires a Model B head gasket on a Model B block. |
Heart | 178-184 | 5.2 :1 |
| A6050B Speed Head (Mike Hart) |
1980s (?) aftermarket head reproduced by Mike Hart Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked "A6050B Speed Head" on top Copy of Model A Ford A-6050-B "Police" head Can use a Model A or B head gasket on a Model A block. Requires a Model B head gasket on a Model B block. |
Heart | 178-184 | 5.2 :1 |
| Model A (Variation 2) |
1930s-40s aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked "Model A" on water hump in raised letters No other markings or date codes May have the manufacturer name "Wohlert" stamped on the water neck gasket surface. Copy of Model A Ford A-6050-B "Police" head Can use a Model A or B head gasket on a Model A block. Requires a Model B head gasket on a Model B block. Buyer Beware: Note that this head marked "Model A" also appears with stock 4.2 ratio wedge combustion chamber |
Heart | 178-184 | 5.2 :1 |
| F2 MF | 1930s aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked "F2", "MF", and "Made in USA" on top Copy of Model A Ford A-6050-B "Police" head Can use a Model A or B head gasket on a Model A block. Requires a Model B head gasket on a Model B block. |
Heart | 178-184 | 5.2 :1 |
| Simmons | Simmons Super Power Head 1930s era aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, located between valves Marked "Simmons Super Power Head" on water hump in raised letters, and "Licensed by Chrysler Motors" on top |
Ricardo Crowfoot |
5.5 :1 | |
| Snyders (unmarked) |
Modern aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Similar to Model A Ford "Police" head Uses a Model B head gasket |
Heart | 5.5 :1 | |
| B-F 5.9 | Brumfield Regular Head 1985-2005 aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Marked "B-F" on top Larry Brumfield design combustion chamber Uses a Fel-Pro 7013 head gasket |
Modified Heart |
5.9 :1 | |
| Snyders (unmarked) |
Modern aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Originals used Bill Stipe design combustion chamber, produced for Snyders by Tod Buttermore Uses a Model B head gasket |
Rounded Modified Heart |
152 | 6.0 :1 |
| Buttermore Winfield |
Modern aftermarket Winfield head Model A, 4 stud water pump Winfield design combustion chamber, modified by Tod Buttermore Uses a Model B head gasket |
Modified Winfield |
6.0 :1 | |
| Hi-Turb "85" Martin & Stoner |
1930s era aftermarket head Model A, 4 stud water pump Metric 18mm spark plugs, over intake valves Marked "Pat P. Hi-Turb" on top Uses a Model A head gasket |
Swirl | 6.0 :1 | |
| Schofield-Hess Flame Control |
1930s era aftermarket head Model A, 4 stud water pump Metric 14mm(?) spark plugs, centered between valves Marked "Schofield-Hess" and "Los Angeles" on top Four standing ribs on water hump Uses a Model A head gasket |
Heart with valley | 6.0 (?) :1 | |
| Winfield | Winfield "Yellow Head" 1930s-40s era aftermarket head Model A, 4 stud water pump Early heads used Champion 7 Metric 18mm spark plugs, Later heads used Metric 14mm spark plugs, Spark plugs located between valves Marked "Winfield" on water hump in recessed letters |
Winfield Standard & Crowfoot |
6.0 :1 | |
| Burtz (unmarked) |
2022 aftermarket head Model A, 4 stud water pump Inch 7/8-18 spark plugs, over intake valves Uses a Best 509G head gasket on a Model A block. Requires a Best 573G Model B head gasket on a Model B block. |
Modified Heart |
6.5 :1 | |
| Winfield | Winfield "Red Head" 1930s-40s era aftermarket head Model A, 4 stud water pump Early heads used Champion 13 Metric 18mm spark plugs, Later heads used Metric 14mm spark plugs, Spark plugs located between valves Marked "Winfield" on water hump in recessed letters |
Winfield Crowfoot |
7.0 :1 | |
| Super Winfield | Super Winfield "Red Head" 1930s-40s era aftermarket head Model A, 4 stud water pump Metric 14mm spark plugs, located between valves Marked "Super Winfield" on water hump in recessed letters |
Winfield Standard |
7.0 :1 | |
| B-F Super | Super Brumfield 1985-2005 aftermarket head Model A, 4 stud water pump Metric 14mm spark plugs, over intake valves Marked "B-F" on top Larry Brumfield design combustion chamber Uses a Fel-Pro 7013 head gasket |
Modified Heart |
7.0 :1 |
Model B & G28T Cast Iron Cylinder Heads:
(Three-bolt Water Pump Provision)
| Part Number or Marking |
Description | Combustion Chamber Shape |
Combustion Chamber Volume (cc) |
Published Compression Ratio |
|---|---|---|---|---|
| B-6050 | Ford USA, Global 1932-38 Standard Production head Model B, 3 bolt water pump Inch 7/8-18 spark plugs, over intake valves Marked with a large "C" on top Also produced by Ford Canada, Ford England, Ford Köln Germany, and Ford GAZ Russia |
Heart | 210-216 | 4.6 :1 |
| F3 | 1930s aftermarket head Model B, 3 bolt water pump provisions Inch 7/8-18 spark plugs, over intake valves Marked with "F3" and "Made in USA" on top Copy of standard production Model B Ford combustion chamber |
Heart | 210-216 | 4.6 :1 |
| M-6050 | Ford GAZ (ГАЗ) Russia 1936-43 Standard Production head Models ГАЗ-AA, ГАЗ-M1, & ГАЗ-67 Model B style, 3 bolt water pump provisions Metric 18mm spark plugs, over intake valves Marked with a large "C" on top, and "M-6050" |
Heart | 210-216 | 4.6 :1 |
| M-ZM-6050 (?) | Ford GAZ (ГАЗ) Russia 1944-53 Standard High Compression head Model ГАЗ-67B Model B style, 3 bolt water pump provisions Metric 14mm? spark plugs, over intake valves |
? | ? | ? :1 |
| G98T-6050 | Ford Köln Germany 1939-42 Standard Production head Model B style, 3 bolt water pump provisions Metric 14mm spark plugs Marked "G98T-6050" on top Same as B-6050 except for spark plug size |
Heart | 210-216 | 4.6 :1 |
| G38T-6050 | Ford Köln Germany 1943-58 Standard Production head Model B style, 3 bolt water pump provisions Metric 14mm spark plugs Marked "G38T-6050" on top What is difference to "G98T-6050" ? |
Heart | 210-216 | 4.6 :1 |
| BG-6050-B | Ford Köln Germany 1930s-1941 Wood Gas Compressor head (Imbert-Holzgas-Anlage) Model B, 3 bolt water pump Inch 7/8-18 (or metric 18mm?) spark plugs Marked "BG-6050-B" on top For use with poured babbitt bearings ("mit ausgegossenen Lagern") |
? | 123-125 | 7.0 :1 |
| G28TG-6050 | Ford Köln Germany 1942 Wood Gas Compressor head (Imbert-Holzgas-Anlage) Model B style, 3 bolt water pump provisions Metric 14mm spark plugs Marked "G28TG-6050" on top For use with shell insert bearings ("mit Lagerschalen") |
? | 94-96 | 8.5 :1 |
| BF-6050 | Ford Dagenham England, 14.9 HP (R.A.C.) 1932-36 Standard Production 3 inch bore head Model B, 3 bolt water pump Inch 7/8-18 spark plugs This head was produced by Ford England for the 2.2L 14.9 HP (R.A.C.) Model BF engine Only fits the Model BF engine block, no others |
Mouse Ears |
100 | 5.2 :1 |
Ford-Produced Compression Ratios:
Five different compression ratio combustion chamber designs were made for the Model A and B standard bore engine by Ford Motor Company themselves.
- 4.2 CR ~ A-6050 Model A
- 4.6 CR ~ B-6050 Model B (marked 'C')
- 5.2 CR ~ A-6050-B Model A Police (marked 'B')
- 7.0 CR ~ BG-6050-B Model B (Imbert-Holzgas-Anlage wood gas compressor thru 1941)
- 8.5 CR ~ G28TG-6050 Model B (Imbert-Holzgas-Anlage wood gas compressor 1942+)
Regarding Main Bearings:
Of the five cast iron combustion chamber designs produced by Ford Motor Company, four were used with Model A and B sized poured Babbitt engine main bearings.
Ford was apparently comfortable using the 7.0 ratio BG-6050-B head with Model B size Babbitt bearings during that era, based on their own releases and catalog descriptions ("mit ausgegossenen Lagern").
Only the 8.5 ratio G28TG-6050 head was used specifically with (Model B/G28T size) steel-backed shell insert bearings ("mit Lagerschalen").
Combustion Volume vs Compression Ratio:
The following graph is derived by plotting the Ford-published data of the combustion chamber volume on the part drawing against the Ford-published data of the compression ratio of each head.
The compression ratio of an unknown flat head can be closely estimated by physically measuring its combustion chamber volume, and then reading the corresponding CR off the graph above.
The estimation would closely approximate the compression ratio that Ford would have claimed for that head using their measurement methods and calculations on a standard bore engine.
The estimation would closely approximate the compression ratio that Ford would have claimed for that head using their measurement methods and calculations on a standard bore engine.
Photo courtesy of Marco Tahtaras
Thanks to Marco Tahtaras for allowing the use of his photo and method of measuring combustion chamber cc's here on Ford Garage!
More related information on Ford Garage:
- For more Model A & B related information, use the Site Search box at the top or bottom of this page.
- Model A & B Cylinder Head Comparison
- Model A Simmons High Compression Cylinder Head
- Model B Russian GAZ Cylinder Head
- Model A Brumfield Cylinder Head and Gaskets
- Model A & B Model C Myth and Terminology
- Model A & B Cylinder Head Gasket Guide comprehensive listing
- Model A & B Cylinder Head Nut Tightening Sequence
- Model A & B Snap-on Cylinder Head Nut Wrench proper torque application tool
- Model A & B Cylinder Head Flatness Requirements by Larry Brumfield
- Model A & B Cylinder Head Gasket Installation Instructions by Larry Brumfield
- Model A & B Cylinder Head and Distributor Pullers by Ron Cloat
- Model A & B Broken Cylinder Head Stud and Bolt Removal
- Model A & B Cylinder Head Stud Removal Tools
April 2013