Detroit Diesel V8 engine

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Detroit Diesel/General Motors V8 Diesel
Detroit 6.2L Diesel
ManufacturerDetroit Diesel, AM General
Production1982-1993 and 1992-current
PredecessorLF9 5.7 liter diesel
SuccessorDuramax V8 engine
Bore6.2L-3.98in, 6.5L-4.06in
Stroke6.2L-3.80in, 6.5L-3.82in
Displacement6.2L/379cid and 6.5L/395cid
Block alloyIron
Head alloyIron
Valvetrain16 OHV
TurbochargerBorg-Warner GM-X series, also available naturally aspirated
Fuel system1993 And older-Mechanical rotary pump. 1994 And newer-Electronic rotary pump
Fuel typeDiesel
Compression ratio21.5:1, Marine 18:1

General Motors introduced a line of Diesel V8 engines for their C/K pickup trucks in 1982. This engine family, designed by GM division Detroit Diesel, was produced by GM through 2000, when it was replaced by the new Duramax line. AM General's subsidiary General Engine Products (GEP) still produces a military variant of this engine for the HMMWV.[1]

The General Motors light-truck 6.2 and 6.5 L Diesel engines were optional in all 1982 through 2000 Chevrolet and GMC C/K series pickup trucks, Suburbans, Blazer/Jimmy, Tahoe/Yukon, vans, motor homes, and the AM General HMMWV. The ready availability and low cost of these engines has made them popular for conversion projects and kit vehicles. These engines are often a popular choice for conversion in Land Rovers, Land Cruisers, and similar vehicles.


The original 6.2 L (379 ci.) Diesel V8 was introduced in 1982 in the Chevrolet/GMC C/K trucks. It was produced through 1993. The 6.2L diesel hit the market as a high-MPG alternative to the V8 gas engine lineup, even while achieving better mileage than the 4.3L gasoline V-6 of the 80s, at a time when power-on-tap wasn't necessarily needed and the market were more focused on the MPG it could achieve.



  • Engine Code: LH6 and LL4
  • Displacement: 6.2L / 379 ci.
  • Bore x Stroke: 3.98 x 3.80 (in.)
  • Block / Head: Cast iron / Cast iron
  • Aspiration: Natural
  • Valvetrain: OHV 2-V
  • Compression: 21.5:1
  • Injection: Indirect
  • Power / Torque (at start): 130 hp (97 kW) @ 3,600 rpm / 240 lb·ft (325 N·m) @ 2,000 rpm
  • Horsepower / Torque (at final): 143 hp (107 kW) @ 3,600 rpm / 257 lb·ft (348 N·m) @ 2,000 rpm
  • Max RPMs: 3,600


The 6.5 L (395 ci.) version was introduced in 1992 to replace the 6.2. Most 6.5s are equipped with a turbo. This engine was never meant to be a power and torque competitor with Ford/International and Dodge/Cummins, but rather a simply designed workhorse engine that made credible power and achieved then-decent fuel economy. The Duramax 6600 replaced the 6.5 in light trucks beginning in 2000, but the 6.5 (6500 Optimizer) is still produced by AM General for the HMMWV.

There are several GM 6.5 liter diesel engine production options. The Turbocharged L56, (VIN "S") was used in all 1/2 ton (1500) and light duty 3/4 ton (2500) trucks. Heavy duty 3/4 ton and 1 ton trucks used the Turbocharged L65 (VIN "F") engine. The L56 is emissions controlled with EGR and catalytic converters. The L65 engine has no EGR, and has no catalytic converter. There is a soot trap on L65 engines that is often mistaken for a catalytic converter. The L49 (VIN "P") and L57 are both normally aspirated engines. L57 is listed as HO or Heavy Duty. Additional RPO codes are LQM (175HP) and LQN (190HP).

Changes were made by GM to the 6.5 in their light trucks for emissions or reliability improvement.
The '92 and '93 model years used a 6.5 specific Stanadyne DB-2 mechanical injection pump. GM replaced the DB-2 with the electronic throttle DS-4 in '94+ vehicles.
In mid 1996 GM implemented a redesigned engine cooling system incorporating twin non bypass-blocking thermostats and a 130GPM water pump. This improved the flow through the block by @70-75% and flow to the radiator 7%.


  • 1994 - 1999 Chevy 2-door Tahoe / GMC Yukon
  • 1992 - 1999 Chevrolet Suburban / GMC Suburban
  • 1992 - 1999 Chevrolet and GMC C/K
  • 2000 Chevrolet and GMC C/K 2500 & 3500
  • 2001 Chevrolet and GMC C/K 3500
  •  ????-Present AM General HMMWV


  • Engine RPO Codes: L49, L56, L57, L65, LQM, and LQN.
  • Displacement: 6.5L / 395 ci.
  • Bore x Stroke: 4.06 x 3.82 (in.)
  • Block / Head: Cast iron / Cast iron
  • Aspiration: Turbocharged (Borg-Warner GM-X series) Also available naturally aspirated.
  • Valvetrain: OHV 2-V
  • Compression: GM Early 21.3:1, GM Late 20.3:1, AMG/GEP Marine 18:1
  • Injection: Indirect
  • Power / Torque (lowest): 180 hp (134 kW) @ 3,400 rpm / 360 lb·ft (488 N·m) @ 1,700 rpm
  • Power / Torque (highest): 215 hp (160 kW) @ 3,200 rpm / 440 lb·ft (597 N·m) @ 1,800 rpm
  • Max RPMs: 3,400

Common Problems

Main bearing web cracks in both 6.2 and 6.5 engines. Reportedly fixed with a combination of improved higher nickel cast iron alloy and lower block re-design including but not limited to a main bearing girdle. These features are in the new for 2007 AM General GEP P400 6500 Optimizer 250-300hp enhanced 6.5 diesel presently being sold to the US Government for the 6 ton armored HMMWV.[1]

Crank failures. Related to age failures of the harmonic balancer, the vibration damped accessory drive pulley, or the dual mass flywheel.

The PMD (Pump Mounted Driver) thermal failures. The PMD is screwed to the DS-4 injection pump on the 1994-2001 GM 6.5 diesel utilizing fuel flow to dissipate heat. The injection pump is mounted in the intake valley (a high heat area). The PMD contains two power transistors that should be cooled by proper contact with the injection pump body. If the pump is not precisely machined to make complete contact with the transistors via the silicone thermal gasket and paste, the PMD is improperly installed without the gasket or paste, the PMD is installed off center with the pump body, or corrosion develops on the mounting surface the PMD will overheat. Several companies manufacture an extension harness and heat-sink kits. These allow an owner or their mechanic to relocate the PMD away from the injection pump to a lower heat environment and/or a place that can get more air flow.


See also