Holley EFI Gen III HEMI Main Harness

Gen III HEMI Engine with Aftermarket Cable Actuated Throttle Body

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Overview:

The Holley EFI Gen III HEMI Main Harness is a precision-engineered wiring solution designed specifically for Gen III HEMI engines equipped with aftermarket cable actuated throttle bodies. This harness serves as the critical interface between your Holley EFI ECU and the engine, enabling seamless control of fuel delivery and ignition timing. Ideal for enthusiasts performing engine swaps or power upgrades, it supports advanced tuning capabilities including power adders like nitrous, superchargers, and turbochargers, as well as compatibility with methanol and water injection systems.

By utilizing most factory sensors, this harness ensures reliable and accurate data transmission while simplifying installation. It is intended to be used alongside Holley EFI injector and coil harnesses, plus two ignition modules, to deliver the most sophisticated fuel and spark management available for the Gen III HEMI platform.

Key Features:

Designed with performance and reliability in mind, the Holley EFI Gen III HEMI Main Harness offers the following key features:

• Dedicated wiring and connectors for Idle Air Control (IAC) motor and Throttle Position Sensor (TPS) tailored for manual throttle body applications
• Enables full control of fuel and spark timing through Holley EFI for enhanced engine performance and tuning flexibility
• Supports advanced power adders including nitrous oxide, superchargers, turbochargers, and is compatible with methanol and water injection setups
• OEM-grade connectors ensure secure, positive fitment and reliable electrical connections
• TXL grade copper wiring offers minimal weight and high temperature resistance with a compact diameter for clean routing
• Factory-style terminations provide strong, durable connections that withstand engine bay conditions
• Split-loom braided routing protects wiring from abrasion and heat while maintaining a professional appearance
• Includes two optional connectors for integration with CAN-based Holley modules, expanding system capabilities
• Specifically engineered to fit and function perfectly with the Gen III HEMI engine platform

Construction & Design:

The harness is constructed using high-quality TXL grade copper wiring, known for its excellent conductivity and resistance to heat and corrosion. The wiring is encased in a high-temperature sleeve with a small diameter, reducing bulk and simplifying installation in tight engine compartments. Holley EFI employs OEM-grade connectors and factory-style terminations to ensure a secure, vibration-resistant connection that maintains signal integrity under demanding conditions. The entire harness is routed through a split-loom braid, providing additional protection against abrasion and heat while delivering a clean, professional look.

Installation & Fitment:

This main harness is designed for straightforward installation on Gen III HEMI engines equipped with aftermarket cable actuated throttle bodies. It requires pairing with Holley EFI injector and coil harnesses as well as two ignition modules to complete the EFI system. Most factory sensors are retained, minimizing the need for additional modifications or sensor replacements. The harness’s OEM-grade connectors and precise fitment reduce installation time and potential wiring errors, making it suitable for both professional shops and experienced enthusiasts.

What's Included:

• Holley EFI Gen III HEMI Main Harness with IAC motor and TPS connectors
• Two optional CAN-based Holley module connectors

Ideal For:

This harness is ideal for automotive enthusiasts and professional tuners upgrading or swapping Gen III HEMI engines with aftermarket cable actuated throttle bodies. It is perfect for those seeking advanced EFI control for fuel and spark management, especially when incorporating power adders such as nitrous, superchargers, or turbochargers. Its compatibility with methanol and water injection systems makes it a versatile choice for high-performance applications requiring precise engine management.

Holley EFI delivers standalone engine management and EFI systems built for everything from engine swaps to serious horsepower builds. With platforms like Sniper, Terminator X, HP, and Dominator, Holley EFI is aimed at enthusiasts who want modern tuning control, data, and drivability—whether it’s a street car, track car, or full-on race program.