This paper describes design enhancements and experimental tests performed on the Detroit Diesel 8V-71T Low Heat Rejection (LHR) Engine. The program objective was to increase brake power approximately 10% while maintaining or reducing brake specific cooling system burden and heat rejection to the engine compartment. In order to achieve these objectives, it was necessary to reduce average right bank exhaust temperatures approximately 23°C to insure acceptable engine durability at elevated power levels. All modifications simultaneously satisfy the rigorous constraints imposed by the U.S. Army's M109 Self Propelled Howitzer and M992 Field Artillery Ammunition Support Vehicle (FAASV). The M992 FAASV is a derivative of the M109 armored vehicle which utilizes the same chassis.Engine fuel supply system, exhaust manifold, turbocharger compressor, and fuel injector modifications were made in order to meet these requirements. A grooveless barrel-faced fire ring design and modified oil control ring configuration were included for improved durability. Experimental engine tests quantified the improvements offered by these changes and validated the final design. A 400 hour North Atlantic Treaty Organization (NATO) durability certification test was used to qualify the final engine design for production release. After passing this test the engine was released to production under model number 7083-7391.