DFC Diesel TH660104LB7SOALBHD Tow/Haul HD Series Speed Of Air Long Block (Standard/Auto) | 2001-2004 GM/Chevrolet 2500HD/3500HD 6.6L Duramax LB7

Features:

• Supports up to 900 horsepower at the flywheel
• Includes Wagler forged connecting rods
• Wagler Stage 1 alternate firing camshaft
• Callies Compstar forged crankshaft installed
• Balanced rotating assembly for smoother performance
• ATI dampener improves engine harmonic stability
• Heavy-duty flexplate handles high torque loads
• All new OEM or equivalent internal parts
• Includes top-end gasket kit for final install
• All rocker arms and pushrods pre-set to spec
• Built for performance and high-load towing
• Backed by 5-year, 160,000 km warranty

Power Through The Job Without Sacrificing Dependability

If your truck sees serious towing, heavy street use, and the occasional need to flex horsepower, the DFC Tow/Haul HD Series Long Block is the build you want on your side. This isn’t your average reman, it’s built to handle up to 900 horsepower while still giving you daily drivability and consistent street manners. Whether you're pulling a loaded trailer across mountain passes or hitting the throttle in a tuned setup, this long block is ready to deliver. It comes fully loaded with premium internals like Wagler forged rods, an alternate firing Stage 1 camshaft, and a Callies Compstar crankshaft for unmatched durability. DFC takes it a step further by balancing the rotating assembly, adding an ATI dampener, and including a heavy-duty flexplate to hold it all together. It’s the kind of build you choose when you expect more than just stock reliability, you want proven strength for every mile and every pull. Backed by a 5-year, 160,000 km warranty, this engine is the definition of overbuilt for real-world abuse.

Built To Withstand The Load And Then Some

The DFC TH660104LB7SOALBHD Tow/Haul HD Series long block is purpose-built for high-output diesel applications between 500 and 900 horsepower. Designed to take everything from daily commuting to heavy towing and full-throttle performance, this long block includes every upgrade found in the Street and Tow/Haul Series plus major internal reinforcements. Wagler forged connecting rods are installed to handle extreme cylinder pressures, while a Wager Stage 1 alternate firing camshaft improves combustion balance and reduces crank stress. The rotating assembly is fully balanced to minimize engine vibration at high RPMs, supported by a Callies Compstar crankshaft and ATI harmonic dampener for smooth operation. A heavy-duty flexplate rounds out the build, providing the torque-handling support needed under heavy loads or hard launches. All major internals meet or exceed OEM standards, including new pistons, rings, and gaskets, giving you a strong base to support aggressive tuning. This long block is ideal for anyone who expects to run high power but still wants the confidence to hit the road or hitch up a trailer without worry.

Fits: 2001, 2002, 2003, 2004 GM/Chevrolet 2500HD/3500HD 6.6L Duramax LB7

Notes:

• Designed for 2001–2004 GM/Chevrolet 2500HD and 3500HD with 6.6L Duramax LB7
• Tow/Haul HD Series is ideal for trucks making 500–900 horsepower
• Includes all upgrades found in Street and Tow/Haul Series engines
• Wagler forged connecting rods handle high cylinder pressures
• Wager Stage 1 alternate firing camshaft improves balance and performance
• Callies Compstar forged crankshaft supports high horsepower builds
• Rotating assembly is fully balanced for smoother operation
• Includes ATI harmonic dampener and heavy-duty flexplate
• All new OEM or equivalent pistons, rings, and gaskets included
• Engine is professionally machined and built to tight tolerances
• Backed by a 5-year or 160,000 km limited warranty
• Professional installation and proper tuning are strongly recommended

Street Series vs Tow/Haul vs Tow/Haul HD

• Street Series: Ideal for daily driving, light work, and diesel enthusiasts. Focuses on reliability upgrades over stock, with head stud and sealing improvements.

• Tow/Haul Series: All Street upgrades plus added performance parts for higher load and towing power. Supports builds up to ~700 HP.

• Tow/Haul HD Series: The most robust option. Adds heavy-duty internals like Wagler rods and a balanced rotating assembly for 800+ HP capability.

Standard/Auto vs Standard vs Auto

• Standard/Auto: Compatible with both manual and automatic transmissions. Offers the most flexibility.

• Standard: Built specifically for manual transmission configurations.

• Auto: Built specifically for automatic transmission setups.