Allis-Chalmers Model "B" specifications

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The figures below are transcribed directly from the factory Allis-Chalmers Model “B” manuals (codes 257986 and TPL-28M). The two booklets’ specification pages are identical, so every value here is corroborated by both sources. These specs describe the 125-cubic-inch production engine; very early “B” tractors (pre-1943) used a smaller engine and may differ.

Engine

Number of cylinders	4
Bore	3⅜″
Stroke	3½″
R.P.M. (full load)	1500
High idle	1800
Firing order	1-2-4-3
Piston displacement	125 cu. in.

Magneto / Ignition

Impulse coupling	Automatic
Lag angle	30 degrees
Timing advance	30 degrees
Point gap	.020″
Spark plug size	14 mm.
Spark plug point gap	.030″ to .040″
Spark plug heat range — gasoline	AC 45 or equivalent
Spark plug heat range — low octane	AC 47 or equivalent

Transmission

Selective sliding gear. Speeds in m.p.h.:

First	2¾
Second	4¼
Third	8½
Reverse	3

Clutch

Type	Single plate dry disc
Diameter	8½″

Brakes & Electrical

Brakes	Enclosed contracting type, foot operated
Battery	6 volt, 95 ampere hour, 13 plate

Capacities

Radiator	2¼ gal.
Oil sump	4 qt.
Transmission and differential	6 qt.
Final drive gears	Each 1½ pt.
Fuel tank	13 gal.

Lubrication note (per manual): add one extra quart of oil in the transmission.

Wheels & Tires

Rear wheel tread	Adjustable 40½″ to 52½″
Front tire size	4:00 x 15
Rear tire size	9 x 24
Rear tire size — optional	10 x 24
Front tire pressure	28 lb.
Rear tire pressure	12 lb.

Belt Pulley (Special Equipment)

Diameter	8″
Face	5½″
R.P.M. (at normal engine speed)	1129

Power Take-Off (Special Equipment)

Spline size	1⅛″
R.P.M. (at normal engine speed)	600
R.P.M. (at engine speed of 1362)	545
R.P.M. (at high idle)	650

All values transcribed verbatim from the Allis-Chalmers Model “B” factory manuals (codes 257986 and TPL-28M); both manuals’ specification pages agree. Fractions and gaps are reproduced as printed. Allis-Chalmers reserved the right to change specifications without notice, so individual tractors may vary by serial-number range — verify against your machine before ordering parts or setting clearances.