DFC Diesel TH6604505LLYSOALB Tow/Haul Series Speed Of Air Long Block (Standard/Auto) | 2004.5-2005 GM/Chevrolet 2500HD/3500HD 6.6L Duramax LLY

Features:

• Built for 2004.5-2005 Duramax LLY trucks
• Rated for towing and hauling up to 500HP
• Includes all Street Series performance upgrades
• Stage 2 camshaft for improved torque delivery
• Mahle Motorsports heavy-duty pistons included
• Manton HD pushrods increase valve train strength
• HD valve springs support higher performance loads
• ARP or OptiTorque head studs for better sealing
• Added crankshaft dowels for better balancer stability
• Includes Total Seal gapless piston rings
• Fully remanufactured to exceed OEM specifications
• Covered by 5-year, 160,000 km limited warranty

Tow With Confidence And Drive With Purpose

If your 2004.5-2005 Duramax-powered 2500HD or 3500HD needs a serious upgrade to match the demands of heavy hauling or daily driving, the DFC Tow/Haul Series Long Block is the engine you’ve been waiting for. This build isn’t just about replacing what's worn out, it's about giving your truck the muscle it deserves. Designed to handle up to 500 horsepower, this long block includes all the proven upgrades of DFC’s Street Series, plus a few heavy-duty reinforcements built specifically for towing and performance. With Mahle HD pistons, Manton pushrods, and a Stage 2 camshaft, this engine delivers better power, smoother throttle response, and more durability under load. Whether you're pulling equipment through steep grades or towing a fifth-wheel across state lines, you can trust this engine to stay cool, strong, and consistent. It’s built by diesel professionals who understand the abuse these trucks take on the job. Backed by a 5-year, 160,000 km warranty, this is the kind of upgrade that turns your truck into a true workhorse.

Heavy Duty Engineering For High Load Performance

The DFC Diesel TH6604505LLYSOALB Tow/Haul Series Long Block is engineered for the 2004.5-2005 6.6L Duramax LLY platform and is rated for up to 500 horsepower at the flywheel. This long block includes all the Street Series enhancements plus key towing-specific upgrades that make it ideal for trucks used in high-demand environments. The block is professionally machined to tight tolerances, fitted with Mahle Motorsports heavy-duty pistons, and assembled with Total Seal gapless piston rings for maximum compression and oil control. A Stage 2 camshaft increases mid-range torque, while Manton HD pushrods and heavy-duty valve springs reinforce valvetrain stability at higher loads. DFC also includes added dowel pins in the crankshaft for better alignment of the harmonic balancer and trigger gear assembly, helping maintain long-term crank stability. ARP or OptiTorque head studs are included depending on availability, offering enhanced clamping force to prevent head lift under boost. Every engine comes with a full top-end gasket kit and pre-set valvetrain components, making install efficient and precise. This long block is ideal for serious diesel owners who demand performance without sacrificing reliability.

Fits: 2004.5, 2005 GM/Chevrolet 2500HD/3500HD 6.6L Duramax LLY

Notes:

• Designed specifically for 2004.5-2005 GM/Chevy 2500HD and 3500HD trucks with the 6.6L Duramax LLY engine
• Tow/Haul Series is ideal for heavy towing, work applications, and trucks pushing up to 500HP
• Includes all upgrades from the Street Series for improved reliability and performance
• Features Mahle Motorsports heavy-duty pistons for added strength under load
• Comes with a Stage 2 camshaft for enhanced torque and throttle response
• Equipped with Manton heavy-duty pushrods and HD valve springs for valvetrain reinforcement
• Crankshaft includes added dowels for balancer and trigger gear alignment
• Includes ARP or OptiTorque head studs depending on availability
• All internal components are new or exceed OEM spec standards
• Engine is machined and assembled to precise tolerances using advanced Rottler equipment
• Rated flywheel horsepower matches factory measurement standards
• Backed by DFC's 5-year or 160,000 km limited warranty for peace of mind

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.