The LB7 Duramax diesel is a 6.6L V8 engine that was developed by DMAX Ltd, a joint venture between General Motors and Isuzu. It was the first engine in the Duramax line, and was known for its high power and torque output, as well as its fuel efficiency. The LB7 was designed to fit in the same space as a gasoline engine, and to achieve this, the turbocharger, fuel-injection pump, and fuel rails were placed in the valley of the engine block. The oil cooler was directly attached to the left side of the cylinder block, and auxiliary equipment was driven by one serpentine belt for ease of service and installation. The engine block was made from a special gray iron alloy and featured a deep-skirt design for increased rigidity and noise suppression.
The Duramax was introduced in 2001 in the GMC and Chevy heavy duty pickups. The first version of the engine was code named LB7. This version was produced from 2001-2004. It can be identified by the 8th digit of the VIN number which should be a 1.
This engine was a great performer but originally suffered from a lot of injector issues. The original injector design would fail and cause hard starts, smoke at idle, and fuel dilution in the oil. The later versions of replacement injectors fixed this issue.