A new configuration 3406 heavy-duty diesel Truck Engine, designated the 3406B, has been developed. The in-line 6-cylinder engine covers the power range of 255-400 hp (190-298 kW) at rated speeds from 1600-2100 rpm. A primary objective of the development program was to provide continued improvement in fuel economy. Emphasis was placed on development of combustion components and systems that could meet both current and future gaseous and noise emission levels. A new fuel system was one of the key elements in meeting the objectives. This paper deals with the design, development and performance aspects of the 3406B Engine.