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Thread: Will 550-606 ECU & Harness work with Coil-On-Plug?

  1. #1

    Default Will 550-606 ECU & Harness work with Coil-On-Plug?

    Looking for guidance with what part numbers, ECU/harness to go with. I'm looking to move from MS3 into a Holley setup. Will the HP 550-606 work with IGN-1A Firecore50 coils? In order to use the smart coils, I would also need the 558-431 harness, correct? Current setup:
    Ford 408W
    Twin 67 Turbos
    6 speed transmissions
    Coil-On-Plug IGN-1A Coils
    15-22 PSI
    Thank you!

  2. #2
    Join Date
    Dec 2009


    Originally Posted by Danny Cabral
    If you already have or you're purchasing a new Holley EFI non-LSx main harness:
    The Holley 558-307 CNP main harness is for Holley's Coil-On-Plug smart coils and LSx ignition coils (nine terminated loose wires into J1B).
    If using Holley's 556-112 CNP coils, the Holley 558-318 CNP coil sub-harness is also required (or the Holley 556-128 CNP Big Wire V8 Kit).
    For LSx coils, Holley 558-307 CNP main harness plugs into two GM 12579355 CNP sub-harnesses or Holley 558-321 LSx coil sub-harnesses.
    If you had a Holley EFI LSx main harness, you wouldn't need the Holley 558-307 CNP main harness or the 558-318 CNP coil sub-harness. (Holley EFI Coil-Near-Plug Ignition Components) (Holley EFI 556-128 Coil-Near-Plug Big Wire V8 Kit) (Holley EFI 558-117 Universal MPFI Coil-Near-Plug Main Harness) (Holley EFI 558-118 Ford Universal MPFI Coil-Near-Plug Main Harness) (Detailed Crank Trigger & CNP/DIS Conversion Information & Reasoning)

    Most people find this document very helpful: (Holley HP & Dominator EFI Component Selection Guide)
    With the Dominator EFI, everything is sold separately. Use Summit Racing's shopping cart for a total price.
    The HP ECU only has four Inputs & four Outputs. If you need more than that, you'll need the Dominator ECU: (Holley HP & Dominator ECU Differences)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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