Holley Adjustable Billet Fuel Bypass Regulator | -6AN | 12-880 SKU: 6669

Holley Adjustable Billet Fuel Bypass Regulator | 6AN Ports | #12-880

Dial in your return-style fuel system with the Holley Adjustable Billet Fuel Bypass Regulator #12-880. Built for precise fuel pressure control, this billet regulator is adjustable from 4-65 PSI and supports a wide range of throttle-body injection, EFI, forced induction, and custom fuel system applications.

Machined from 6061-T6 billet aluminum, the Holley #12-880 features a black anodized base with a clear anodized top for a clean, professional finish. It includes a factory-installed low-pressure spring for many throttle-body injection systems, plus a secondary spring for EFI systems that require higher fuel pressure.

Note: This regulator features 6AN O-ring ports but does not include AN fittings. For a more complete installation, check out our WH Adjustable Fuel Bypass Regulator Kit, which includes the regulator, fittings, and fuel pressure gauge.

• Adjustable 4-65 PSI Range – Supports many TBI, EFI, and custom fuel systems

• Return-Style Fuel System Design – Built for systems using a return line back to the tank

• 6AN O-Ring Ports – Features 6AN inlet, outlet, and return ports

• Fittings Not Included – AN fittings must be purchased separately

• Dual Spring Setup – Includes low-pressure and high-pressure spring options

• 6061-T6 Billet Aluminum Construction – Precision-machined for strength, durability, and long service life

• Anodized Finish – Black anodized base with clear anodized top for a clean, professional appearance

• Boost Referenced – Supports 1:1 boost reference capability for forced induction applications

• Gauge Port Included – Features a 1/8" NPT port for adding a fuel pressure gauge

• Manifold Reference Fitting Included – Allows pressure reference connection where required

Pressure Range Details

This regulator includes two spring options for different fuel system requirements:

• 4-15 PSI Spring – Factory installed for many low-pressure throttle-body injection systems

• 16-65 PSI Spring – Included for EFI systems that require higher fuel pressure

Always follow the fuel pressure specifications provided by your EFI system, fuel system, or engine management manufacturer.

Important Fitting Note

The Holley #12-880 regulator includes 6AN O-ring inlet, outlet, and return ports, but it does not include the AN fittings needed to connect your fuel lines.

For a cleaner, more complete setup, we recommend our WH Adjustable Fuel Bypass Regulator Kit, which includes:

• Holley adjustable bypass regulator

• Required fittings

• Fuel pressure gauge

• Mounting hardware

This saves time during installation and helps ensure you have the key components needed to properly plumb your return-style fuel system.

When Do I Need a Bypass Fuel Pressure Regulator?

A bypass regulator is used when your fuel system needs stable, adjustable pressure with excess fuel returned to the tank.

Common applications include:

• Throttle-Body Injection Systems – Supports many low-pressure TBI fuel setups

• EFI Conversions – Helps maintain proper fuel pressure when upgrading to electronic fuel injection

• High-Pressure EFI Systems – Included secondary spring supports systems that demand higher fuel pressure

• Forced Induction Applications – 1:1 boost reference capability helps pressure rise with boost

• Custom Fuel Systems – Ideal for upgraded pumps, return-style fuel plumbing, and modified engine combinations

• Performance Broncos – Helps keep fuel delivery consistent under changing load and driving conditions

Additional Information

• Holley part number: 12-880

• Adjustable pressure range: 4-65 PSI

  • Factory-installed spring range: 4-15 PSI

  • Included secondary spring range: 16-65 PSI

• Regulator style: bypass / return-style

• Inlet port: 6AN O-ring

• Outlet port: 6AN O-ring

• Return port: 6AN O-ring

• Gauge port: 1/8" NPT

• Material: 6061-T6 billet aluminum

• Finish: black anodized base with clear anodized top

• AN fittings not included

Take control of your fuel system with a Holley billet bypass regulator built for precise pressure control, return-style plumbing, and dependable performance.

Control fuel pressure with a Holley billet bypass regulator featuring 4-65 PSI adjustment, 6AN ports, boost reference support, and EFI-ready performance.