DFC Diesel TH660104LB7SOALB Tow/Haul Series Speed Of Air Long Block (Standard/Auto) | 2001-2004 GM/Chevrolet 2500HD/3500HD 6.6L Duramax LB7

Features:

• Built for up to 500 horsepower output
• Includes Stage 2 performance camshaft
• Mahle Motorsports heavy-duty pistons installed
• Manton HD pushrods for added strength
• HD valve springs support higher performance
• Total Seal gapless piston rings standard
• Screw-in injector cups improve reliability
• Crankshaft dowels for harmonic balancer stability
• All new OEM-grade internal components
• ARP or OptiTorque head studs included
• Top-end gasket kit included with long block
• Backed by 5-year, 160,000 km warranty

Push Your Truck Farther With Confidence Built In

If your 2001–2004 Duramax 2500HD or 3500HD needs a serious powerplant upgrade, the DFC Tow/Haul Series Long Block is built to handle the job. Designed for heavy towing, performance applications, and real-world work trucks, this engine packs premium components and proven durability into every build. Unlike a basic replacement, this long block includes performance-minded upgrades like a Stage 2 camshaft, Mahle Motorsports heavy-duty pistons, and Manton HD pushrods, all engineered to support up to 500 horsepower at the flywheel. You’ll also get the reliability of screw-in injector cups, a known weak point in stock LB7s, and added dowels in the crankshaft to keep your balancer and trigger gear rock-solid. Whether you're hauling loads cross-country or just want peace of mind under the hood, this engine is built to work hard and hold together under pressure. With a 5-year, 160,000 km warranty and nothing but name-brand internals throughout, it’s a serious upgrade for diesel owners who rely on their truck every day. From reliability to raw strength, this long block doesn’t cut corners, and neither should you.

Designed To Withstand Torque Heat And Heavy Load

The DFC Diesel TH660104LB7SOALB Tow/Haul Series long block delivers a precision-built solution for 2001–2004 GM and Chevrolet trucks running the 6.6L LB7 Duramax. This engine includes all the upgrades found in DFC’s Street Series models, but steps it up with components chosen for higher horsepower and long-haul towing demands. At the core is a professionally machined and bored block, built to accept oversized pistons and outfitted with Mahle Motorsports HD units for added strength. A Stage 2 camshaft provides better valve timing for power and torque delivery, while Manton HD pushrods and upgraded valve springs improve valvetrain stability under load. Total Seal gapless rings increase compression and reduce blow-by, helping the engine operate efficiently under high stress. Added dowels in the crankshaft stabilize the harmonic balancer and trigger gear assembly, improving long-term engine balance and precision. Screw-in injector cups resolve a common failure point found in early LB7 models, adding peace of mind during extended operation. From daily towing to hard-working commercial use, this long block is engineered to support performance up to 500 HP while keeping durability at the center of its design.

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 Series is ideal for towing and performance applications
• Rated to support up to 500 horsepower at the flywheel
• Includes all upgrades found in the Street Series long block
• Features Mahle Motorsports heavy-duty pistons for added strength
• Includes Stage 2 performance camshaft for improved power delivery
• Equipped with Manton HD pushrods and heavy-duty valve springs
• Crankshaft includes added dowels for harmonic balancer stability
• LB7 variant includes screw-in injector cups to prevent common failure
• Block is professionally machined and bored for oversized pistons
• Remanufactured using all new OEM or equivalent internal components
• Backed by a 5-year or 160,000 km limited warranty
• Professional installation and proper engine break-in 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.