Objective: This paper documents the 400 hour NATO qualification endurance test for the Detroit Diesel Corporation (DDC), 8V71TA/LHR (turbocharged, aftercooled/low heat rejection) diesel engine rated at 395 kw (530 bhp) at 2500 RPM for potential M109 Self-Propelled Howitzer (SPH) application. The engine was developed under the DARPA (Defense Advanced Research Projects Agency) Advanced Ceramic Technology Insertion Program, managed by U.S. Army TACOM (Tank-automotive and Armaments Command). The test was performed by DDC in accordance with the standards set forth in NATO AEP-5 (Allied Engineering Publication). The ACTIP program objective was to demonstrate the production viability of selected ceramic engine components and investigate the manner in which the ceramic technology integration would enhance the engine's performance and durability. Effects on performance and durability are reported herein. Four engine systems were developed with ceramic components for the ACTIP program. These included: (1) the valve actuation system which included monolithic Silicon Nitride exhaust valves and clevis pins, (2) the fuel injection system which incorporated a monolithic Silicon Nitride injector needle valve, (3) the power transfer system design which included pistons with plasma sprayed thermal barrier coatings and (4) the air handling system which was modified to include abradable compressor and turbine housing coatings. The ACTIP engine successfully completed the 400 Hour cyclic durability test. Final inspection of the engine components at the completion of the test showed there were no problematic conditions which would have precluded continuation of testing. Inspection of the ceramic components revealed no component distress. Overall, an additional 67 kw (90 HP) was obtained over the current M109 SPH 8V71-T engine's rated power. Comparing the ACTIP engine with the current production engine showed fuel consumption improvements of up to 5.7% at the same power levels.