Product Description
Wehrli WCF100342 3.5in Intake Horn – 01-04 LB7 Duramax
The WEHRLI CUSTOM FAB WCF100342 3.5IN INTAKE HORN is a high-flow replacement for the restrictive factory LB7 turbo inlet on 2001–2004 GM 6.6L Duramax trucks. Designed to work with the stock IHI turbo and drop-in IHI-style upgrades, this horn improves airflow into the compressor for quicker spool-up, lower drive pressure, and noticeable horsepower gains without requiring tuning.
Key Features & Benefits
- High-flow 3.5" turbo intake horn for 2001–2004 LB7 Duramax applications.
- Compatible with factory IHI turbochargers and most drop-in IHI-style upgraded chargers.
- Works with OEM airbox or aftermarket performance intake systems.
- Improves turbocharger spool-up and throttle response, especially under load and towing.
- Supports additional horsepower on tuned and turbo-upgraded trucks.
- Durable powdercoated finish in your choice of WCFab colors for a show-quality engine bay.
- Direct bolt-on design with no tuning required for installation.
Fitment
This Wehrli intake horn fits the following vehicles:
- 2001–2004 Chevrolet Silverado 2500HD / 3500 6.6L Duramax LB7
- 2001–2004 GMC Sierra 2500HD / 3500 6.6L Duramax LB7
- Engine code: LB7 6.6L Duramax (VIN 1)
Designed for use with OEM-style IHI turbos and drop-in IHI replacement turbos. For S300/S400 style single or compound kits, see compatible Wehrli turbo kits on CPP Diesel.
What's Included
- 3.5" WCFab intake horn assembly for LB7 Duramax
- Stainless mounting hardware
- Intake horn gasket
- Custom powdercoated finish in your selected color
- Installation instructions (via manufacturer documentation / video)
Recommended Companion Parts
For a complete LB7 airflow package, pair this intake horn with these Wehrli upgrades from CPP Diesel:
- WEHRLI CUSTOM FAB WCF100693 2001-2004 LB7 DURAMAX Y-BRIDGE KIT – High-flow 3" Y-bridge and cold-side pipe to complete the charge-air path from intercooler to engine.
- WEHRLI CUSTOM FAB WCF100349 DRIVER (HOT) SIDE 3" INTERCOOLER PIPE KIT FOR 2001-2004 LB7 DURAMAX – Upgraded hot-side intercooler pipe to match your high-flow Y-bridge and intake horn.
- WEHRLI CUSTOM FAB WCF100023 FUEL PRESSURE RELIEF VALVE DELETE KIT FOR 01-04 GM DURAMAX LB7 ENGINE – Clears space and ensures proper fuel rail configuration for larger Y-bridge and charge pipe setups.
- WEHRLI CUSTOM FAB WCF100119 3IN DOWN PIPE FOR 01-04 CHEVROLET 6.6L LB7 DURAMAX – Frees up exhaust flow off the turbo to complement your improved intake tract.
Performance & Driveability
By replacing the restrictive stock intake horn with a smoother, larger 3.5" design, the WCF100342 helps the turbocharger breathe easier. On strong tune files with the factory-style IHI turbo, customers commonly see gains in the 10–15 HP range, with higher potential gains (up to roughly 20 HP) on setups running upgraded drop-in turbos and supporting mods. The result is improved midrange pull, better top-end airflow, and a more responsive truck without sacrificing reliability.
Specifications
| Brand | Wehrli Custom Fabrication (WCFab) |
|---|---|
| Part Number | WCF100342 |
| Product Type | Turbo intake horn / turbo inlet |
| Inlet Size | 3.5" (3 1/2 inch) intake horn |
| Engine | 6.6L Duramax LB7 |
| Model Years | 2001–2004 GM 2500HD / 3500 |
| Turbo Compatibility | Factory IHI turbo and most drop-in IHI-style upgrade turbos |
| Air Intake Compatibility | OEM airbox or aftermarket performance intake systems |
| Construction | Fabricated, high-flow design with show-quality powdercoat finish |
| Tuning Required | No – bolt-on upgrade |
Installation Notes
- Direct bolt-on replacement of the factory intake horn on LB7 Duramax engines.
- Basic hand tools required; allow extra time to work around factory components in the engine bay.
- Always verify color choice and fitment before ordering, especially on heavily modified trucks.
Frequently Asked Questions
Do I need custom tuning after installing the WCF100342 intake horn?No. This intake horn is designed as a bolt-on airflow upgrade that does not require any ECU recalibration to operate correctly. Tuning can further optimize performance, but it is not mandatory for safe use.
Will this intake horn work with my stock airbox?
Yes. The WCF100342 intake horn is compatible with the factory airbox as well as most aftermarket intake systems for the 2001–2004 LB7 Duramax. Always double-check clearances on highly customized setups.
How much horsepower can I gain from this upgrade?
On otherwise stock-turbo trucks with strong tuning, it is common to see gains in the 10–15 HP range. Trucks running upgraded drop-in IHI-style turbos and supporting airflow mods can see closer to 20 HP improvements from the reduced restriction at the turbo inlet. Actual results depend on overall build, tuning, and environmental conditions.
Can I custom order the intake horn color?
Yes. WCFab offers a wide selection of standard and premium powdercoat colors so you can match your truck's theme or engine bay. Select your preferred color option from the drop-down menu when ordering.
Is this intake horn compatible with S300 or S400 turbo swaps?
This horn is primarily intended for factory-style IHI turbochargers and compatible drop-in upgrades. If you're running or planning an S300 or S400 turbo setup, consider Wehrli's dedicated S300/S400 single or compound turbo kits for proper fitment and performance.
