Mack Engine Specifications

by Phil Whitmer

Mack engines are designed and assembled at the company's Hagerstown, Maryland plant. They're used in commercial Mack trucks, including the popular line of Mack off-road trucks. Mack engines were the first to allow heavy trucks to use a five-speed transmission.


The Mack Maxidyne MP8 USO7 diesel engine is an in-line, six-cylinder, turbocharged, direct fuel injected motor with a displacement of 780 cubic inches. It has 24 poppet valves, steel dual-ring pistons and a single overhead cam. Its factory dry weight is approximately 2,560 pounds.


The USO7's peak rating is 485 horsepower at 1,500 to 1,900 rpm, with a governed rating of 340 horsepower at 2,100 rpm. It has a bore of 5.16 inches and a stroke of 6.22 inches, with a compression ratio of 16:1. It produces 1,700 ft.-lbs. of torque at 1,100 to 1,500 rpm, with a low idle speed of 650 rpm and a high idle speed of 2,100 rpm.


The MP8 USO7 features a cast iron block, cast aluminum flywheel housing and a forged, carbon steel crankshaft. It has a cooled exhaust gas recirculation system and a Mack PowerLeash engine brake with a retarding power of 435 horsepower at 2,100 rpm.

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