SKU: HLY558-456
UPC: 090127101780
MPN: 558-456
The HOLLEY Pro-Dash Harness Un-terminated IO (SKU HLY558-456) is a professional-grade dash wiring harness engineered for custom engine management and aftermarket gauge installations. This un-terminated harness kit ships with individual pins, plugs, and wires pre-assembled, allowing builders and technicians to configure connections precisely for their specific ECU and instrumentation requirements without factory connector constraints.
The un-terminated design is the defining advantage of this harness for custom applications. Rather than being locked into pre-molded connectors, installers gain full flexibility to terminate connections exactly where sensors, switches, and display units are positioned on the dash. Weighing 2.95 lbs and measuring 10.5 x 3.9 x 11.3 inches, the harness accommodates complex wiring layouts in tight engine bays and custom chassis. The included pins and plugs are industry-standard automotive connectors, ensuring reliable contact and repeatable crimps across multiple installations.
This harness is purpose-built for hot rod builders, performance tuners, and race teams integrating HOLLEY fuel injection systems or modern aftermarket ECUs into older vehicles or custom platforms. Professional mechanics favor un-terminated harnesses because they eliminate the guesswork of working around fixed connectors and reduce the risk of installing components in the wrong location. Technicians can verify sensor placement, plan wire runs, and terminate connections during final tune-up rather than during initial assembly.
HOLLEY's reputation in fuel injection and engine management systems makes this harness a natural choice for builders committed to quality wiring infrastructure. The combination of pre-assembled backbone wire lengths with user-terminated connections strikes the balance between convenience and customization—no need to source individual wires, yet no loss of installation flexibility. Ideal for restorations, LS swaps, and carbureted-to-injected conversions where OEM harnesses do not fit or offer insufficient sensor capacity.
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