WEHRLI CUSTOM FAB WCF100119 3IN DOWN PIPE FOR 01-04 CHEVROLET 6.6L LB7 DURAMAX

Wehrli WCF100119 3" Down Pipe for 01-04 Chevrolet 6.6L LB7 Duramax

The WEHRLI CUSTOM FAB WCF100119 3" Down Pipe is a high-flow, bolt-on upgrade for your 2001–2004 Chevy/GMC 6.6L Duramax LB7. Designed for use with the OEM IHI charger and Stealth series drop-in turbos, this 3" mandrel-bent turbo downpipe improves exhaust flow, helps lower EGTs, and sharpens throttle response while maintaining a clean, factory-style fitment.

Each pipe is finished with a high-temp ceramic coating and pre-installed heat wrap to control radiant heat in the engine bay and protect nearby components during heavy towing, performance driving, or competition use.

Key Features & Benefits

• Direct-fit 3" mandrel-bent LB7 turbo downpipe for 2001–2004 GM 6.6L Duramax LB7 trucks.
• Compatible with OEM IHI turbocharger and Stealth series drop-in IHI-style upgraded chargers.
• High-temp ceramic coating and pre-installed heat wrap help manage EGTs and under-hood heat.
• Improved exhaust flow for better turbo response, efficiency, and overall drivability.
• Bolt-on upgrade that installs in the factory location with no custom fabrication required.
• No ECM tuning required – simple hardware upgrade for stock or mildly modified trucks.
• Compatible with both standard and California-style OEM exhaust flanges at the downpipe connection.
• Replaces restrictive factory downpipe sections to support future turbo and intake upgrades.

What's Included

• Wehrli WCF100119 3" LB7 turbo downpipe assembly.
• High-temp ceramic coating applied to the pipe.
• Pre-installed heat wrap on the downpipe.
• Installation hardware as supplied by WCFab (fasteners / small parts may vary by production run).

Vehicle Fitment

• 2001–2004 Chevrolet Silverado 2500HD / 3500 – 6.6L Duramax LB7
• 2001–2004 GMC Sierra 2500HD / 3500 – 6.6L Duramax LB7

Installation & Tuning Notes

• Direct bolt-on replacement for the factory turbo downpipe on LB7 applications.
• Compatible with OEM exhaust systems using both standard and California-style flanges at the downpipe connection.
• Designed for use with OEM IHI turbochargers and Stealth series drop-in IHI-style turbos.
• Replaces GM downpipe section corresponding to OEM part numbers 97223168 and 97246408.
• No tuning is required; however, combining this downpipe with additional airflow and fuel upgrades may benefit from custom calibration.
• Professional installation recommended – access to the turbo area behind the engine can be tight on LB7 trucks.
• Emissions & shipping note: Many distributors list this part as not legal for sale or use on emissions-controlled vehicles in California or other CARB-regulated states and/or as not shippable to California. Always verify and comply with your local emissions regulations.

Pair With These Wehrli Upgrades

For a complete LB7 airflow package, pair the WCF100119 3" downpipe with these Wehrli Custom Fab upgrades available at CPP Diesel:

• WEHRLI CUSTOM FAB WCF100693 2001-2004 LB7 DURAMAX Y-BRIDGE KIT – High-flow 3" Y-bridge and cold-side intercooler pipe to create a full 3" charge-air tract.
• WEHRLI CUSTOM FAB WCF100712 2001-2004 LB7 DURAMAX STAGE 3 HIGH FLOW INTAKE BUNDLE KIT – Includes Y-bridge, intercooler pipes, intake, and this 3" downpipe in one matched system.
• WEHRLI CUSTOM FAB WCF100589 01-04 CHEVROLET 6.6L DURAMAX LB7 2IN STAINLESS UP PIPE KIT W/GASKETS – TWIN TURBO – Ideal for compound/twin turbo LB7 builds needing high-flow up-pipes.
• WEHRLI CUSTOM FAB WCF100590 01-04 CHEVROLET 6.6L DURAMAX LB7 2IN STAINLESS UP PIPE KIT W/GASKETS – SINGLE TURBO – High-flow up-pipes for single-turbo LB7 setups.
• WEHRLI CUSTOM FAB WCF100023 FUEL PRESSURE RELIEF VALVE DELETE KIT FOR 01-04 GM DURAMAX LB7 ENGINE – Provides clearance for larger Y-bridge and turbo inlet components on aggressive LB7 builds.

Specifications

Frequently Asked Questions

Yes. The WCF100119 3" downpipe is designed specifically for 2001–2004 LB7 Duramax trucks using the OEM IHI turbocharger. It also works with Stealth series drop-in IHI-style chargers that retain the factory style turbine outlet.

No tuning is required for this part by itself. It is a bolt-on hardware upgrade that improves exhaust flow and turbo response using the factory emissions sensors and control strategy. If you combine this downpipe with additional fueling, turbo, or intake upgrades, custom tuning may be beneficial to get the most performance from your setup.

The downpipe is physically compatible with both standard and California-style OEM exhaust flanges at the connection point. However, many manufacturers and resellers list this part as not legal for sale or use on emissions-controlled vehicles in California or other CARB-regulated states. Always review and follow your local laws before purchasing or installing.

Yes, most owners notice a slightly more aggressive exhaust note and more pronounced turbo whistle, especially under load or acceleration, due to the less restrictive 3" design. Overall sound level will also depend on your remaining exhaust system, muffler, and tailpipe configuration.

In most cases, yes. The WCF100119 uses the factory-style connection at the downpipe flange, so it will typically mate to any exhaust system designed to fit an OEM downpipe on 2001–2004 LB7 trucks. If you are running a custom or heavily modified exhaust, minor adaptation may be required.

The downpipe reuses the factory turbo outlet mounting location and connects to the OEM-style exhaust flange. Any hardware included with the WCF100119 kit should be used during installation; we also recommend inspecting the turbo outlet gasket and replacement hardware on older or high-mileage trucks to ensure a leak-free seal.