The Official Studebaker Reference Guide 1938-40 Truck K Series No pictures at this time Truck Model Engine Used Engine Model Cooling Cap. Qts. K10 (1 Ton) own OT 16 K15 (1 1/2 - 2 Ton) own IT 16 K15M (1 1/2 - 2 Ton Note1) own IT 16 K20 (2-3 Ton) Hercules JXB 21 K20M (2-3 Ton Note1) Hercules JXB 21 K20MR (2-3 Ton Note1) Hercules JXB 21 K25 (2 1/4 - 4 Ton) Hercules JXD 21 K25M (2 1/4 - 4 Ton Note1) Hercules JXD 21 K25MR (2 1/4 - 4 Ton Note1) Hercules JXD 21 K30 (3-5 Ton) Hercules WXC3 23 K30M (3-5 Ton Note1) Hercules WXC3 23 Note#1: Cab Over Engine, Short Wheelbase Serial Number plate Location: n/a. Production Information: n/a General Engine Specifications: Engine Model # of Cyl - Bore & Stroke Displacement Compression Max Torque H.P. Max Brake H.P. Oil Capacity Qts. OT 6 - 3 5/16 x 4 3/8 226 6.00 148@1200 75@3200 5 1/2 IT 6 - 3 5/16 x 4 3/8 226 6.00 163@1200 76@3200 5 1/2 Engine Tune-Up Specifications: Model Firing Order Spark Plug Gap Point Gap Valve Seat Angle Intake Tappet Exhaust Tappet Intake Stem Clearance Exhaust Stem Clearance Valve Spring Pressure lb @ inch OT 153624 .025 .020 45 .016C .016C .002-.003 .0025-.004 130 @ 1 3/4 IT 153624 .025 .020 45 .016C .016C .002-.003 .003-.004 123 @ 1 3/4 Note#2 Note#2: After engine # IT-21001, 130 @ 1 3/4 Piston, Rings & Bearings: Model Piston Clearance Comp. Ring Gap Oil Ring Gap Crankpin Dia. Rod Bearing Clearance Main Journal Dia. Main Bearing Clearance Crank Endplay OT .0005 .013 .013 2.1865 - 2.1875 .0005 - .002 2.4995 - 2.5000 .0005 - .0025 .003 - .006 IT .0005 .013 .013 2.1865 - 2.1875 .0005 - .002 2.4995 - 2.5000 .0005 - .0025 .003 - .006 Table of Contents | Chapter 6 - Studebaker Trucks