Great Northern Challengers

The Great Northern Railway bought two 4-6-6-4s from its subsidiary, the Spokane, Portland & Seattle Railroad These two ALCO-built, former SP&S road numbers 903 and 904, were designated Class Z-6 and were given road numbers 4000 and 4001 on the Great Northern. They had four 23 x 32 cylinders, 69" drivers, a boiler pressure of 250 psi, a tractive effort of 104,500 lbs and weighed 621,000 pounds.

The two Great Northern "Challengers" were sold back to the SP&S, number 4000 in 1946 and 4001 in 1950.

Specifications for Class Z-6

Wheel Arrangement: 4-6-6-4

Length: 119' - 8"

Drivers: 69" dia.

Weight on Drivers: 436,000 lbs

Locomotive Weight: 621,000 lbs

Locomotive & Tender Weight: 1,014,700 lbs

Grate Area: 152.3 sq ft

Cylinders (dia. x stroke): (4) 23" x 32"

Boiler Pressure: 250 psi

Tractive Effort: 104,500 lbs

Tender Capacity:

Water: 20,000 gals.

Fuel Oil: 6,000 gals.

Specifications for Class Z-6
Wheel Arrangement:	4-6-6-4
Length:	119' - 8"
Drivers:	69" dia.
Weight on Drivers:	436,000 lbs
Locomotive Weight:	621,000 lbs
Locomotive & Tender Weight:	1,014,700 lbs
Grate Area:	152.3 sq ft
Cylinders (dia. x stroke):	(4) 23" x 32"
Boiler Pressure:	250 psi
Tractive Effort:	104,500 lbs
Tender Capacity:
Water:	20,000 gals.
Fuel Oil:	6,000 gals.

References

The Great Northern Railway by Charles and Dorothy Wood (Pacific Fast Mail)
Locomotives of the Empire Builders by Charles F. Martin (Normandie House)
Great Northern Railway Historical Society
1781 Griffith
Berkley, MI 48072