Ford Model A 1928, 1929, 1930, 1931 Specifications

 

Wheel Specifications

Material Steel

Diameter 1928-29 21", 1930-31 19"

Rim Drop center type; width, 1928-29 2-3/4", 1930-31 3"

Number of Spokes 30, 1/4" diameter

​

Tire Specifications

Size 1928-29, 4.50" x 21" 1930-31, 4.75" x 19"

Recommended Tire Pressure 35 Lbs

Station Wagon 5" x 21" or 19", pressure 40 lbs

Tread Width 21" = 3.75", 19"3.90"

​

Front Brake Specifications

Braking Power Front, 40%; Rear, 50%

Drum Diameter 11" +/- .010"

Drum Width 1-3/4"

Brake Shoe Length 14"

Brake Shoe Width 1-1/2"

Brake Shoe Lining Thickness 3/16"

Brake Shoe Material Woven wire & asbestos

Brake Rod Length 51-7/16" thru 51-1/2"

​

Rear Emergency Brake Specifications

Drum Diameter 9-5/8"

Drum Width 1-3/4"

Brake Shoe Length 28-3/4"

Brake Shoe Width 1"

Brake Shoe Lining Thickness 3/16" (original), 1/8" (ours)

Brake Shoe Material Woven wire & asbestos

​

Front Axle & Spindle Specifications

Material Chrome alloy forging

Tensile Strength 125,000-145,000 PSI

Caster 5" (forward tilt)

Toe In 1/16" +/- 1/32"

Camber 1-13/16"

Spindle Bolt Diameter .8125" +/- .005"

Spindle Bolt Length 5-5/16"

Spindle Bolt to Bearing Clearance .001"-.002"

​

7-Tooth Steering Gear Specifications

Turning Radius 17' (34' diameter)

Steering Gear Ratio 1928-29, 11-1/4:1

Steering Wheel Diameter 1928-29, 17-1/2"

Pitman Arm Length 6-7/8" hole center to ball center

Ball End Angle to Shaft 14°

Sector Shaft Bearing Clearance .001"-.002"

​

2-Tooth Steering Gear Specifications

Turning Radius 17' (34' diameter)

Steering Gear Ratio 1930-31, 13:1

Steering Wheel Diameter 1930-31, 17"

Pitman Arm Length 6-7/8" hole center to ball center

Ball End Angle to Shaft 14°

Sector Shaft Bearing Clearance .001"-.002"

​

2-Tooth Steering Gear Housing Casting Markings

DatesGemmerFord

February - May 1929“GEMMER” & “PAT. PDG.” in raised lettersRaised “F” on the side

February - May 1929“GEMMER” & “PAT. PENDING” in indented lettersRaised “F” on the side

April 1929 - Mid 1930“GEMMER” & “PATENTED” in indented lettersRaised “F” on the side

January 1930 - EndNo IDIndented “A-3550-C” on the engine side

January 1930 - EndNo IDIndented “A-3550-C” on the engine side & raised 5/16" or 9/16" letter “F” on the other side

Except for minor machining differences, all the above housings are virtually identical mechanically
& all new parts furnished will fit each one.

Ford & Gemmer were the two manufacturers of the 2-tooth steering box. All parts are interchangeable, exceptthe worm gear, 2 races & 2 bearings. The Ford box has a large “F” on the outside where the worms are located. This change was made in December of 1930 (See page 518 Service Bulletins). The Ford box used a #9 roller bearing, while the Gemmer box used a #13 roller bearing. This also changes the taper on the bearings & races. The only parts available today are for the Gemmer box; therefore, if you have the Ford box with #9 roller bearings & it becomes necessary to change any of the 5 parts, then you must convert to all 5 of the Gemmer components (A3524CD, (2) BB3571, A3553D, BB3552)

​

600W Oil Usage Specifications

Transmission 1 pint

Rear End 1-1/2 Quarts

7-tooth Steering Box 7-3/4 ounces

2-tooth Steering Box 4-1/2 ounces

​

Rear Axle Specifications

Type Three quarter floating

Material Special Ford carbon manganese steel

Gear Ratio 3.78:1 (34-9) Early 1928: 3.7:1 (37-10) Trucks: 4.11:1 (37-9) 1928-29 Roadsters: 3.54:1 (39-11)

Pinion Bearing Cup Double taper roller type B4616

Bearing Cup B4222

Differential Bearing B4221

Ring Gear 8.4" pitch diameter, 1-3/16" wide teeth

Axle Shaft 1-1/8" diameter, 1.128"-1.130"

Dimension From Housing Flange to Bearing Shoulder Before 1929-1.370"-1.372", After 1929-1.365"-1.367"

ID of Wheel Hub 3.188"-3.190": max. wear 3.185"

Axle & Drive Shaft Seal B4245

Inner Axle Seal B4245

Differential Lubricant 600W

New Bearing Torque 20 foot pounds

Bolt Torque 35 foot pounds

Axle Backlash .010"-.015"

Axle End Play .015"-.020"

Length of Full Spline 2-1/2"

Spline Minor Diameter .901"-.911"

Spline Outer Diameter 1.090"-1.091"

Pinion Bearing Torque 15-20 foot pounds

​

Front Spring Specifications

Material Chromium steel alloy

Front Spring Leaf Width 1-3/4"

Front Spring Free Length 30-13/16" to 30-15/16"

Leaf Thickness 1-31/32" to 2-1/16"

Spring Off Car- Height from Top to Bottom as Sitting on Floor 6-15/16" to 7-1/16"

Spring Off Car- Center of Eye to Eye 30-5/8" to 30-13/16"

Ford blueprints called for each leaf to be coated with 
a thick paste of graphite ground in oil.

​

Cylinder Head Specifications

1928 Head 4.3:1 compression ratio, 47.3 HP, 242cc displacement. Compression in individual cylinders: 80, 85, 83, 82 PSI

1930 Head 4.1:1 compression ratio, 44.3 HP, 258cc displacement. Compression in individual cylinders: 77, 79, 82, 79 PSI

Normal Listed Compression A6050A, 75 pounds; A6050B, 110 pounds; B6050, 90 pounds

Head Nut Torque 50 foot pounds

​

Engine Specifications

Rated Horsepower 24.03 SAE

Brake Horsepower 40 HP at 2200 rpm (Model AF 28 at 2000 rpm)

Firing Order 1-2-4-3

Compression Ratio: 4.11:1

Compression Pressure: A6050A head, 76 PSI A6050B head, 110 PSI B6050 head, 90 PSI

Piston Displacement 200.5 cubic inches

Bore 3.876" (Model AF: 3.050")

Stroke 4.250"

Torque 128 foot pounds at 1000 rpm

Cylinder Offset from Crankshaft Centerline 1/8"

Crankshaft to Camshaft Centerline 4.155"

​

Piston Specifications

Displacement 200.5 cubic inches

Material Aluminum

Weight 1 lb. 1-7/8 oz. (476.8 grams)

Variance in Weight of Pistons +/- 2 grams

Weight with Rings Installed 1 lb. 4-1/2 oz. (581.2 grams)

Weight with Rings & Pin 1 lb. 8-3/4 oz. (701.7 grams)

Diameter 3.8745" (Bore 3.875")

Length 3-29/32"

Piston Skirt .001: small on the top than on the bottom of the skirt

Piston Pin Hole .9996" to .9998" diameter

Piston Pin Diameter 1.0001" to 1.0004"

Pin Length 3.536" to 3.546"

Compression Height (Top of piston to pin centerline) 1-29/32"

Variation in Piston Compression Height .003" to .005"

Piston Pin Bushing ID .992", OD 1.0675"

Length 1.593"

Pin Fit in Rod Bushing .0003" max

Pin Fit in Piston .0002" to .0005" shrink fit

Pin Bore Parallel to Head of Piston +/- .001"

Piston Fit in Cylinder .002" max

​

Piston Ring Specifications

Ring Diameter Same as piston, 3.875" stock

Ring Groove Depth, 7/32", Width - Upper 2, 1/8" Lower, 5/32"

Ring Taper .001"- narrower at the top than the bottom

Ring Clearance in Groove .001" to .002"

Ring End Gap Top .012" to .015"; Middle .010" to .012"; Lower .008" to .010"

All piston ring sets are US made Grant or Hastings brands with 3 rings. The gap of the rings must not line up, MAC's suggests keeping them about a 1/4 turn from each other.

​

Connecting Rod Specifications

Material Steel forging

Weight 1 lb, 6 oz.

Balance Weight 552 grams +/- 1 gram, crank end 198 grams +/- 1 gram, pin end

Length 7-1/2" center to center

Crankshaft Bearing 1-1/2" diameter, 1-5/8" wide

Piston Pin Bearing 1" diameter, 1-5/8" wide

Bearing Side Clearance .008" to .012"

Pin Side Clearance .040" to .053" between pin bosses

Piston Pin Clearance .0005"

Crankshaft Clearance .001"

Bearing Cap Bolt Torque 40-50 foot pounds.

Connecting rod is assembled with oil dippers toward camshaft.

​

Camshaft Specifications

Shaft Diameter 7/8"

Bearing Diameter 1.560"

Block Bore Diameter 1.561"

Bearing Clearance (Max.) .003"

Bearing Length Front, 1-3/4"; Center, 2"; Rear, 1"; 4th (1928), 7/8"

Lift of Cam .030" (Model B: .339" exhaust; .334" intake)

Duration 236º

Lobe Center Angle 113-1/2º

End Play Spring Tension Approximately 35 pounds

Timing Gear Mounting Flange 2-5/16" diameter, 5/16" thick

Camshaft Material Special Ford carbon manganese steel

Cam Shaft Gear Bakelized material

Number of Gear Teeth 50

Camshaft Gear Type Spiral teeth

Gear Backlash .003" to .005"

Gear Rotation Speed 1/2 of crankshaft

Camshaft Straightness .0005" to .001"

Variation in Eccentricity of Pitch Diameter of Gear Teeth .0015"

Variation in Maintaining Center Distance of Mating Gears +/- .001"

Gear Tolerances in Regular Spacing of Teeth 0.0"

​

Crankshaft Specifications

Material Ford carbon manganese steel

Weight 28 pounds

Length 26"

Diameter 1.624" main bearings; 1.499" crank pins

Length of Main Bearings Front & Center, 2"; Rear 3"

Length of Crank Pins 1-5/8"

Crank Pin Taper & Roundness .0005" to .001"

Total Main Bearing Surface 11-1/2 square inches

Rear Flange Thickness 3/8"

Crankshaft Gear 25 spiral teeth

End Clearance .004" to .007"

Main Bearing Clearance .001"

Crankshaft Straightness .0005" to .001"

Main Bearing Cap Torque 80-100 foot pounds

Distance from Top Surface of Front Cross Member to Crankshaft Centerline 2-33/64"

​

Flywheel Specifications

Weight 63 lbs., 4 oz. (Model B 52 to 55 lbs.)

Balance Within 15 in./oz.

Ring Gear Shoulder Diameter 12.470"

Ring Gear Outside Diameter 14.2"

Number of Ring Gear Teeth 112

Ring Gear to Starter Drive Ratio 11.2: 1

Flywheel Bolt Torque 65 foot pounds

Pilot bearing hole is concentric with crankshaft flange shoulder within .002" TIR (Total Indicator Reading).

Clutch mounting surface & clutch disc surface must run true to crankshaft within .005" TIR (Total Indicator Reading).
Clutch mounting shoulder diameter must be concentric with crankshaft flange diameter within .005" TIR (Total Indicator Reading).

Flywheels provide momentum to keep the crankshaft spinning. As the flywheel spins faster, a vibration will occur if it’s out of balance. It’s best to have your flywheel, with clutch & pressure plate, balanced so that when you place in the clutch disc & reinstall the pressure plate it will retain balance.

​

Valve Specifications

Lift .287" with .015" clearance

Seat Angle 45º

Seat Width 3.32"

Stem Diameter .311"

Valve Length 5.677"

Head Diameter 1.537"

Valve Opening Diameter 1-3/8"

Port Diameter 1-3/8"

Clearance, Exhaust Valves in Guides .002"

Clearance, Intake Valves in Guides .001" to .0015"

Valve Lifter Clearance .010" to .013"

Lifter Diameter Clearance .0015"

Valve Guides .3135" ID; .5938" OD; length 2.125" (early 2.375")

Valve Spring 1.022" OD; free length 2-15/16"; comp. length 
2-1/14" (57-64 lbs.); tension (closed) 34 to 38 lbs.

Valve Lifter A6500A (used with A camshaft), length 2.486"; 
head diameter 1.117".

Valve Timing Intake opens 7-1/2º before Top Dead Center; closes 48-1/2º after Bottom Dead Center. Exhaust opens 51-1/2º before Bottom Dead Center; closes 4-1/2º after Top Dead Center.