This coil harness is built for early Gen III HEMI coils — the style that requires spark plug wires, used before Chrysler phased in the later plug-boot coil design starting in 2006. It connects Gen III HEMI engines to Holley HP EFI and Dominator EFI for advanced fuel and spark control, and supports tuning with power adders like nitrous, superchargers, or turbos, plus methanol and water injection.
Key Features:
- Take full control of fuel and spark on a Gen III HEMI swap or power upgrade
- Compatible with nitrous, superchargers, turbos, methanol, and water injection tuning
- Designed in fit and function specifically for the Gen III HEMI platform
- TXL-grade copper wiring with minimal weight and a high-temp, small-diameter sleeve
- Factory-style terminations for a strong, secure connection
- OEM-grade connectors for a correct, positive fit
- Routed through split-loom braid for protection and a clean look
Specifications:
- Application: Gen III HEMI, early coils (require spark plug wires)
- Compatible ECUs: HP EFI, Dominator EFI
- Wiring: TXL-grade copper
- Part Number: 558-310
Holley EFI does not currently support the HEMI's Variable Valve Timing — engines with VVT will run, but cam timing reverts to the mechanical default. The Multi-Displacement System (MDS), used for factory fuel economy, does not need to be connected when converting to Holley EFI.
Compliance: This part is legal for sale and use on Racing Use Only Vehicles — competition vehicles that are not registered and never operated on the street. It is against the law to install this part on an Emissions Controlled Vehicle (1966-and-newer California-certified or 1968-and-newer federally certified vehicles).
FAQ
How do I know if I have early or late Gen III HEMI coils?
Early coils require spark plug wires. Later coils (phased in starting in 2006) have no plug wires and connect with two boots directly to the plugs in the cylinder head.
Does this harness support the HEMI's Variable Valve Timing?
Not currently — the engine will run with VVT installed, but cam timing reverts to its mechanical default. Holley's R&D team has not yet released an accessory harness for the VVT actuator.
Do I need to connect the Multi-Displacement System (MDS)?
No, MDS was designed for factory fuel economy and doesn't need to be connected when switching to a Holley EFI system.
Can this support power adders?
Yes, it's compatible with tuning for nitrous, superchargers, turbos, and methanol/water injection.
Is this legal for street use?
No, it's legal for Racing Use Only vehicles and not legal for sale or use on pollution-controlled vehicles.