6.6L LB7 Duramax Specifications And Information

The 6.6L LB7 Duramax was the initial diesel engine offered in GM trucks and SUVs. It included a 32-valve, double overhead cam aluminum cylinder head design. Plus, it boasted a Bosch electronically controlled commonrail direct injection system. Additionally, it had a variable geometry turbocharger. The LB7 was produced from 2001-2004. It was used in Chevrolet and GMC HD pickups and SUVs.

Duramax specification

Here’s a summary of the 6.6L LB7 Duramax specs:

Engine Type

The 6.6L LB7 Duramax engine is a 4-stroke, diesel engine. It has internal lubrication, a cooled EGR system, and electronic common rail fuel injection. The block is cast iron and the cylinder heads are aluminum. Commonly, it has 8 cylinders in V-configuration with 8 valves per cylinder. This engine meets EPA emissions standards with two-stage Eaton emission-control and air-to-fuel ratio control. EGR and exhaust pressure regulation also help.

It can be found in Chevy and GMC trucks (2001-2004) and some mid-2000s vans and SUVs. Horsepower is 220-300 at 2500-2600 RPM. Torque is 520-710 lb.-ft.

Horsepower and Torque

General Motors produces the 6.6L Duramax Diesel V8 engine for use in GM pickup trucks and SUVs (2003 to the present). It produces an impressive power of up to 445 horsepower and 910 lb.-ft. of torque.

The specs vary between model years. For engines from 2003-2006, it averages between 300-310 horsepower and 520-610 lb.-ft. of torque due to more stringent emissions control systems.

It has a single overhead camshaft (OHC), sixteen valves, and uses common-rail direct injection technology. This enhances mileage significantly compared to earlier diesel engines.

The engine also features an electronic exhaust gas recirculation system (EGR) as well as Variable Geometry Turbo (VGT). This helps the turbocharger spool faster and makes it easier to control emissions in warmer climates.


The 6.6L LB7 Duramax was crafted for high performance. It boasts great fuel economy and reliability. Widely praised and staple in the diesel engine industry. It features a single overhead cam for improved durability.

Here are the specifications of the 6.6L LB7 Duramax:

Block and Head

The 6.6L LB7 Duramax V8 is crafted from cast iron and ductile iron cylinder liners. It has a V-shaped design, with two banks of 4 cylinders each. Each cylinder has a single overhead camshaft that operates 4 valves. The intake and exhaust valves are shared by a pair of cylinders. They also share a single casting for the cylinder head and intake manifold. The compression ratio is 17:1. This is made possible by a deep skirt design that adds oil control and strength. Coolant flows through the block from back to front. This helps keep the hottest area of the engine cool.

Pistons and Connecting Rods

The pistons in the 6.6L LB7 Duramax engine are special. They are made from marine grade material. Each piston comes with two rings. The top one is chrome-plated, the less one is cast iron napier. The third ring is an oil ring.

The connecting rods are also marine grade material. They have an elongated small end which fits perfectly to the piston pin boss. Each rod has bearing inserts pre-fitted and pressed in.

The LB7 Duramax has two bolt mains and a one piece rear seal. It is stronger and more durable than GM’s two piece seals.

Camshaft and Valves

The LB7 Duramax 6.6L engine has a cast iron cylinder head. This increases thermal capacity and rigidity, making it more durable.

The aluminum camshaft has a power-to-torque ratio of 2.25. This gives a great balance of low end torque and high end power.

Roller rocker arms open the eight valves. This allows for higher valve spring pressures, reducing friction between the rocker arm and valve stem tips. It also increases flow in the exhaust ports.

The camshaft is chain driven and centrally located. This gives perfect timing for all four cylinders and a uniform overlap for maximum efficiency. The chain has reduced tension too. This helps keep noise down, making it quieter than other LB7 models.

Fuel System

The 6.6 Duramax LB7 engine uses a common rail direct injection fuel system. This system can reach up to 23,000 psi of fuel pressure. This pressure helps the LB7 atomize the fuel better and boosts its power and performance. It has two high pressure fuel pumps and an in-tank low pressure lift pump.

Let’s investigate these components more closely:

Fuel Injection System

The 6.6L LB7 Duramax has an advanced fuel injection system. It can deliver up to 30,000 psi of fuel pressure. The Bosch ECM (electronic control module) is programmed for the engine and sends signals to the high-pressure pump for timing and fuel delivery. It coordinates info between the throttle positioning sensor, mass air flow sensor and other parts. It also regulates the injector spray for efficiency. The pressure reduces at lower engine speeds or under light loads for smoother performance.

An oil pre-heater keeps the diesel fuel warm until injected into the combustion chamber. The 6.6L LB7 Duramax has a secondary “lift pump” with intake filters, which can be serviced separately from the main pump. This keeps the injectors clean and running reliably.

Fuel Pressure and Delivery

Fuel pressure and delivery are essential for any vehicle. This system controls how much gasoline flows from the tank to the engine for peak performance.

For regulation, various parts are needed:

  • Fuel pump: pushes the pressure and volume needed.
  • Regulator valve: controls pressure in one point systems.
  • ECU: acts as an automatic “brain” that watches engine performance, temperature, and pressure. Also sends signals to other parts such as injectors.
  • Fuel injectors: tiny valves that release precise amounts of atomized gasoline into cylinders.
  • Fuel lines: hoses carry pressurized gasoline from the pump.

A working fuel delivery system brings efficient performance and combustion. This ensures optimal driving and safety.

Exhaust System

The LB7 6.6L Duramax exhaust system? It’s made up of a turbocharger, downpipe, manifold, catalytic converter and muffler. The turbocharger uses exhaust gas to spin the turbine. This helps pump air into the engine. The downpipe and manifold aid with air flow and reduce back pressure. The catalytic converter reduces emissions and the muffler lessens the noise.

Let’s take a closer peek at the exhaust system features:

Exhaust Manifold

The 6.6L LB7 Duramax diesel engine’s exhaust manifold is made of steel. It connects to the cylinder head’s exhaust outlet. Pieces of tubing are welded together to customize the manifold’s shape and size. Flanges, nuts, bolts, and gaskets seal the gaps. Back pressure is regulated, and too much fuel is prevented from entering the cylinders.

The air flows directly across all cylinders, making a consistent and smooth flow. This improves the vehicle’s exhaust system, efficiency, power output, and fuel economy.

Exhaust Brake

An exhaust brake is an extra device added to the vehicle’s exhaust system. It adds backpressure, reducing engine power and creating resistance to slow the vehicle down. It works off the vehicle’s existing exhaust system, so it’s a cost-effective choice for commercial vehicles.

Exhaust brakes are often used on heavy duty trucks, but also other vehicles. The valves control the engine’s intake and exhaust air flow, for precise backpressure management. This is regulated by a switch in the cab, so you can adjust it as needed.

The advantages of having an exhaust brake include:

  • Improved fuel efficiency
  • Less wear & tear on the brakes
  • Extended engine lifespan
  • It reduces temperatures from higher rpm revving and ensures cooling time after hard accelerations or rapid decelerations – all of which add up to better performance.

Cooling System

The 6.6L LB7 Duramax has a critical cooling system. It is in charge of getting rid of heat from the engine block and other elements. This apparatus is made up of radiators, water pumps, thermostats, coolant hoses and other parts.

Let’s take a closer look and explore how each component of the cooling system functions:


The Duramax 6.6LB7 has a unique radiator. It has one row of 72mm tubes and two big plastic tanks. It has a patented re-circulation loop to reduce emissions, improve fuel economy, and reduce noise. It also has an extra-large electric cooling fan to draw hot air from the engine bay and increase performance in harsh conditions.


The 6.6L Duramax cooling system is made up of components that keep the engine running at a safe temperature. The aluminum radiator takes cooling air through metal passageways. This helps the hot liquid cool and save energy for when cooler air isn’t available.

The coolant travels through an intake manifold, turbocharger, and hoses to the engine block. Here it cycles through the chambers and then exits the block, going to a water pump. This pushes the liquid back through the system. The vaporized coolant goes to a reservoir tank and can be processed or re-circulated as needed.

Additionally, every LB7 Duramax diesel engine has an electronic fan clutch for extra cooling power when needed.


The LB7 Duramax diesel engine had two transmission options. The manual was a 6-speed NV4500. GM created the automatic, a 4-speed 4L80E. Both offer good strength.

Let’s examine the features of these transmissions:

Allison 1000

The Allison 1000 in the 6.6L LB7 Duramax is a heavy-duty automatic transmission. GM designed it to handle the power and torque of the LB7 Duramax. It’s one of the most reliable transmissions available.

The Allison 1000 features three planetary gear sets, five clutch packs, and electronic shift controls. This allows for smooth shifts, high torque capacity, and improved fuel economy. Compared to traditional four-speed automatics, this transmission offers smoother shifting, increased fuel economy, and improved durability.

The Allison 1000 also offers a wide-ratio gear selection. First gear has 5:86:1 for added low-speed performance. This means it can climb steep grades with ease. It has a 5th direct drive gear at a 1:1 ratio plus an overdrive 6th gear. This maximizes fuel economy when cruising down the highway or on long stretches of road trips.

Torque Converter

The LB7 Duramax engine can be found in GMC and Chevrolet vehicles from 2001-2004. It’s a 6.6L, V8 turbo diesel with 397 lb-ft of torque. It has a five-speed Allison 1000 series transmission with an electronically controlled torque converter. This allows for smoother shifting and improved fuel economy. The transmission is designed to be easily upgraded to high performance levels.

The Allison 1000 torque converter connects the engine and transmission. It does this by engaging different gear sets based on input from sensors. These sensors detect changes in drive train tension or load. This makes sure that accessories stay in sync when shifting.

The Duramax LB7 also has two sets of clutch discs. They handle periodic and rapid input changes. The computer system monitors the speeds between the discs. If it detects an abnormally small difference, it issues a shift command to alter the gear ratio.

For ultimate performance, upgrade your turbo diesel motor with Suncoast Diesel’s 12″ torque converter. It’s certified up to 900 hp & 1750 lb-ft tq!

Power Take Off

The 6.6L LB7 Duramax engine is known for its power and reliability. It has a PTO capability too. Let’s discuss specifics of the PTO system, including features and capabilities. This way, you can decide if it fits your needs.

PTO Gearbox

The 6.6L LB7 Duramax engine has a Power Take Off (PTO) gearbox. It provides power to an external load. The PTO gearbox consists of two pieces made of die-cast and machined housing. It has three parallel gears. These usually drive a hydraulic pump or fan. One or two gears may drive auxiliary devices, like pumps and blowers. It is at the rear corner of the engine block.

The three gears are arranged in line with the crankshaft. The splined shafts of all three gears are linked together by a roller-bearing circle clip. This allows torque to be transferred from one gear to one or more other gears. As more components are added, each draws torque from only one gear. If the component fails, it takes torque from another gear until it is repaired.

Inspect and maintain components connected to the PTO Gearbox, as per OEM guidelines. Fill the PTO Gearbox with fluids recommended by OEM before operation. Re-fill between services. Meet inspection criteria before using the PTO Gearbox. Any problems should be cleared up with a service professional. Unless authorized, don’t use it until problems are fixed.

PTO Shafts

Power Take Off (PTO) shafts are an essential part of a powertrain assembly in a 6.6L LB7 Duramax diesel engine. The PTO shaft enables the engine to work with external components, such as winches, air compressors, and pumps. PTO shafts come in four sizes – SAE 1, 4, 6 and 8 – and should be chosen based on their application requirements.

The largest size – SAE 1 – is best for applications that need high power output or torque. These include tow trucks and certain commercial uses. It offers up to 350 Horsepower (HP) at 2400RPM and can work from 1200 RPM up to 3200 RPM.

SAE 4 PTO shafts give maximum power outputs up to 200 HP at 2400 RPM, with an operating sensitivity between 1000 RPM and 3200 RPM. This size is ideal for agricultural vehicles (tractors or combines) and fire apparatuses that need more pulling force than a smaller model.

SAE 6 PTO shaft provides 50 Horsepower (HP) at 2400RPM, with a lower operating sensitivity of 900-2400RPM. It is perfect for small utility vehicles (ATVs/UTVs) or applications that need controllable speed without compromising performance.

SAE 8 PTO is mainly used for smaller applications, like electric winches on off-road Jeeps or lightweight utility vehicles. It has low power thresholds of 35Hp @ 2400RPM and a narrow operating tolerance of 1200-1800 RPM. It’s important to review your needs before selecting a PTO shaft when designing your Duramax 6.6L LB7 engine assembly.


The 6.6L LB7 Duramax engine is a powerhouse. It offers great endurance and power. Accessories can be added to further boost its performance. Let’s explore the various accessories available for this engine. We’ll look at the pros and cons of each one:


The 6.6L LB7 Duramax diesel engine features a turbocharger. It is made up of a turbo housing, a turbine wheel and a compressor wheel, all connected by a shaft. The compressor wheel sucks in the air, compresses it and sends it to the intake manifold. The turbine wheel is powered by exhaust gases, making the compressor spin faster, thus increasing engine power.

There are two turbochargers used on the LB7: variable geometry and fixed geometry ones. The variable geometry has movable vanes to adjust air flow. This type was used on 2002-2004 V8 engines with LLY codes. It maximizes performance in any driving condition. Fixed-geometry turbos don’t have moving parts. They compress the air, sending it at a high pressure rate to the engine’s intake manifold. They generate less boost than variable-geometry turbos due to their impellers, but are more durable due to their set parameters and lack of complex components. These were used from 2004 until 2006 when Duramax moved to EGR equipped models.


The intercooler, also known as a charge air cooler or aftercooler, cools hot, pressurized air from the turbocharger. This cooled, denser air boosts power. It also reduces exhaust gas temperature (EGTs).

The 6.6L LB7 Duramax diesel engine uses an air-to-air type intercooler. This has an aluminum core and end tanks, hoses and tubing, clamps and connection points. The “hot” side connects to the turbocharger compressor housing and plenum chamber. The “cold” side connects to the intake manifold.

Performance upgrades on the 6.6L LB7 Duramax engine can benefit from a new or upgraded intercooler. An upgraded one is larger than stock. It may have aluminum construction to improve heat dissipation and flow characteristics. The larger size increases flow due to its increased surface area. It can be less obstructed by debris. Aluminum construction is stronger and lighter. It also provides better airflow, depending on the build requirements and budget. Consumers can choose the best intercooler for their application, taking into account the elevation they will be running in.

Air Intake System

An upgraded air intake system is a must for any 6.6L LB7 Duramax engine. Without it, the engine cannot breathe well. This hinders power and performance. Air intake systems draw in cool, oxygen-rich air to mix with fuel and create power.

The favorite air intake system for this engine is the cold air intake (CAI). These come in different sizes and shapes. They draw the coolest, most oxygen rich air into the engine’s cylinders for efficient combustion. CAIs have an enclosed box to reduce turbulence and keep out heat, debris and moisture. They may have water savers, filters, or mounts for nitrous oxide systems.

Other aftermarket air intakes that help 6.6L LB7 Duramaxes are:

  • Short ram intakes (SRT)
  • Turbocharged intakes (TIP)
  • Intercooler intakes (ICT)
  • Force induction kits (FIT)

Each type offers benefits based on their design. These are great for various usage requirements.

Frequently Asked Questions

What type of engine is the 6.6L LB7 Duramax?

The 6.6L LB7 Duramax is a diesel engine manufactured by General Motors.

What is the power output of the 6.6L LB7 Duramax?

The 6.6L LB7 Duramax produces 300 horsepower and 520 lb-ft of torque.

What is the fuel economy of the 6.6L LB7 Duramax?

The 6.6L LB7 Duramax has a fuel economy of 18 mpg city/22 mpg highway.