SMG "Big Boy" Drop-in Fuel Pump for 14+ Silverado/Sierra

SMG “Big Boy” Drop-In Low-Side Fuel Pump Module

The factory low-side fuel system can become the restriction long before a properly built Gen V truck combination reaches its potential. The SMG Big Boy was developed to bridge the gap between the stock module and a full auxiliary or standalone fuel system while preserving an OEM-style installation.

Each module begins with an original-equipment-style pump assembly and is upgraded in-house with a high-output Walbro 535 pump, reinforced internal wiring and factory-style pressure regulation. The completed assembly drops into the tank without cutting the tank, splicing the vehicle harness or replacing the factory supply line.

Why the Big Boy Works

• High-output genuine Walbro 535 “Hellcat” fuel pump
• Modified OEM-style fuel-pump module for factory-like fit
• Upgraded internal wiring for high-current reliability
• No tank cutting, external sump or vehicle-harness splicing
• Compatible with pump gasoline and ethanol fuels, including E85
• Hand-built and function-tested by SMG before shipment

Proven Fueling Capacity

The Big Boy has been tested in a Silverado/Sierra platform supporting more than 750 wheel horsepower on E85 with stock LT4 injectors, an LT4 high-pressure fuel pump and a 32% cam fuel lobe. That result reflects one complete vehicle combination; actual capacity depends on commanded pressure, fuel type, injector and high-pressure-pump capability, tuning, boost and the rest of the fuel system.

The module is also a strong foundation for customers planning to add an SMG auxiliary fuel system later. The drop-in pump handles the OEM-style primary supply while the aux system adds capacity for more demanding builds.

Vehicle Fitment

Designed for 2014–2018 Chevrolet Silverado 1500 and GMC Sierra 1500 V8 models. Some early-2019 trucks use the previous-generation tank and module design and may also fit. Confirm that the truck is the legacy-body configuration before ordering for 2019.

Select the correct cab/bed configuration:

• Extended Cab / Crew Cab
• Standard Cab Long Bed
• Standard Cab Short Bed

Cab and bed selection matters because GM used different module and tank configurations. Do not choose solely by model year.

What to Expect During Installation

• Remove the original in-tank pump module
• Transfer the existing fuel-level sender when the selected module does not include a new sender
• Install the Big Boy module in the factory location
• Reconnect the factory wiring and fuel supply connection
• Update the calibration for the new pump’s pressure and volume capability

The module can operate on a stock calibration, but professional tuning is strongly recommended to obtain the intended performance and maintain stable fuel pressure.

Tuning and Operating Notes

• Review desired pressure, maximum pressure, pump duty-cycle, FSCM and ECM fuel-pressure tables
• GM-style regulators commonly begin bypassing near 5 bar, approximately 72 psi
• Many high-output combinations perform well with commanded low-side pressure in the 50–60 psi range
• Avoid performance driving below one-quarter tank; high pump volume can outpace saddle-tank transfer under sustained demand
• Work with a qualified tuner familiar with Gen V GM truck fuel-system control

Fuel Compatibility

• Approved for pump gasoline and ethanol-based fuels, including E85
• Not approved for methanol, aggressive race-fuel additives or other fuels not compatible with the module’s internal seals

Build Quality, Lead Time and Warranty

Each Big Boy module is assembled and tested in Texas. This is a made-to-order product; allow approximately 5–7 business days for assembly before shipment. The shipping method selected at checkout affects transit time after the module is completed.

The original purchaser receives a 90-day limited warranty against manufacturing defects. Coverage does not include physical damage, improper installation, tuning errors or damage caused by unapproved fuels. The module must be returned to SMG for inspection before warranty authorization.

Recommended Supporting Products

• SMG Silverado/Sierra Flex Fuel Kit
• SMG Truck/SUV Auxiliary Fuel System
• LT4 injectors and high-pressure fuel-pump upgrades for compatible applications