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  The Duramax Diesel engine is found in all heavy-duty General Motors (GM) trucks manufactured from 2001 and on. The Duramax is structurally an Isuzu engine, but the electronics were designed by GM. The engine comes in a 4.5 liter and a 6.6 liter; the 6.6 liter has five different generations: LB7, LLY, LBZ, LMM and LML.
  
  

4.5 Liter LMK

• The 4.5 liter LMK engine is slated to replace the large gasoline V-8s in all GM trucks, vans and SUVs. Production was set for 2010, but financial difficulties stopped the production and no release date has been set. While GM has not yet released the official numbers, this engine is said to meet or exceed 310 horsepower.
  
  

6.6 Liter LB7

• The first lineup of Duramax engines was the LB7. The LB7 was the replacement for the 6.5 liter diesel engine that GM formerly used. This engine was produced from 2001 to 2004. The first release of the LB7 produced 235 horsepower at 2,700 RPM, but it was increased to 300 horsepower at 3,100 RPM in 2004.
  
  

6.6 Liter LLY

• The LLY is the second generation of the Duramax Diesel; it was released in 2004 to replace the LB7, but a change in 2006 optimized horsepower. The original release of the LLY produces 310 horsepower at 3,000 RPM. A change of compression and cylinder heads boosts it to 320 horsepower at 3,000 RPM.
  
  

6.6 Liter LBZ

• The LBZ replaced the LLY model Duramax in 2006 and was used through 2007. It is structurally the same engine as the LLY, but it has some electronic modifications to increase performance. This engine produces 360 horsepower at 3,200 RPM.
  
  

6.6 Liter LMM

• The LMM model of the Duramax line was put into use in mid-2007. This engine was mainly produced to meet the new, stricter diesel regulations in 2007. The LMM is still capable of producing better output regardless of the stricter laws; it produces 365 horsepower at 3,100 RPM.
  
  

6.6 Liter LML

• The newest addition to the Duramax line is the LML. This engine is fitted in all 2011 diesel GM trucks. This engine is designed to increase power and cleanliness as it is the most powerful and has the lowest emissions of any Duramax engine. This engine produces 397 horsepower at 3,000 RPM.