2001-2004 LB7 Duramax S400/Stock Twin (Compound) Turbo Kit

Compound boost that still spools like stock

This Wehrli kit adds an S400-frame turbo ahead of the factory-style turbo, so the two work as a compound pair. Wehrli rates the platform as capable of about 1000 rear-wheel hp, depending on the turbos and fuel system you pair it with.

Wehrli aims it at work trucks and towing rigs: more power and better exhaust-temperature control with turbo response close to stock. Its suggested pairings run from an S475 over a stock IHI (up to about 750 rwhp with supporting mods) to an S480 over a Stealth 64 drop-in (900+ rwhp), each with a built Allison recommended.

Who it's for

LB7 owners who tow hard and want a big power step without giving up low-rpm response.

Key specs (per Wehrli)

What's included

• 5 in. intake with dry filter and pre-filter cover
• 3.5 in. cold side charge pipe and 3.5 in. turbo inlet horn
• 3 in. one-piece Y-bridge and 3 in. cold side intercooler pipe
• 3 in. steel hot side crossover and 4 in. steel downpipe, ceramic coated, with heat wrap
• Atmosphere turbo pedestal with built-in oil return
• Coolant overflow tank with hoses, fittings and low-coolant sensor
• Stainless oil feed and drain lines
• Silicone boots, T-bolt and V-band clamps; powder-coated finish

Fitment notes

• Fits 2001-2004 Chevrolet Silverado / GMC Sierra 2500 HD and 3500 with the 6.6L LB7 Duramax.
• The passenger-side battery must be removed or relocated.
• Wehrli says this kit needs custom tuning to run correctly.
• California: Wehrli does not ship this part to California.

Professional install available at Powertech Diesel, Idaho Falls — call 208-542-7793.