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Thread: Holley Dual Sync Distributor Wiring

  1. #1

    Default Holley Dual Sync Distributor Wiring

    I'm installing a Holley Dual Sync Distributor to my Sniper EFI. I just received the wire harness adapter, but I'm not sure how the wiring goes. The instructions that came with the Sniper EFI, and the ones that came with the distributor are not very clear. I'm running an MSD Digital 6AL. I have the purple & green wire hooked up to the single purple wire, which is connected to the tach out wire of the MSD box per the instructions. The new distributor wire harness adapter plugs into the distributor plug. The other side of the adapter has one plug containing the purple wire. There is also a red/white striped wire and a green wire, both unterminated. So, do I unplug the original purple & blue wires coming off the main harness, and plug in the single purple wire from the distributor? Where do I connect the red/white striped and green wires to? Thanks!
    Last edited by 30rat; 12-19-2016 at 11:22 PM.

  2. #2
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    Currently, the Sniper EFI instruction manual has the wrong wiring diagram for the Holley 558-493 Adapter Harness.
    https://www.youtube.com/watch?v=ld9ml6e6P6Q (This Sniper EFI YouTube video has the correct wiring diagram @ 2:33 minutes.)
    You might have to contact Holley Tech Service (LINK) if you have further questions about the wiring instructions.

    http://documents.holley.com/199r11031r.pdf (Holley Sniper EFI Instruction Manual - For my own reference.)
    http://documents.holley.com/199r11193.pdf (Holley Sniper EFI Quick Start Manual - For my own reference.)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #3
    Join Date
    Oct 2016
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    Middle River, MD
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    Quote Originally Posted by 30rat View Post
    I'm installing a Holley Dual Sync Distributor to my Sniper EFI. I just received the wire harness adapter...
    Would you possibly share where you were able to locate the harness? Thanks for that video link Danny.
    Last edited by rel3rd; 12-20-2016 at 07:43 AM.

  4. #4

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    Quote Originally Posted by rel3rd View Post
    Would you possibly share where you were able to locate the harness? Thanks for that video link Danny.
    Thanks for the replies. It was originally thought that hooking up the Holley Dual Sync was plug & play but it isn't? The main harness has a purple & blue wire with a small plastic connector, that's plugged into another connector that has one purple wire that has an unterminated end that you connect to the gray wire of your MSD box. That's all per the instructions. I had to contact Holley to have them send me the harness wire adapter for the Dual Sync distributor, which I described above. It came with no instructions and the ones that came with the Sniper EFI & distributor don't show how or where to connect it, plus the wire colors are wrong. The video says you just plug it in? You can't because one end has a plug you connect to the distributor, and the other end of the adapter only has one purple wire with a plug and a red & green with unterminated ends. I have an idea of where to hookup the purple, which would be to the one that is hooked up now to my gray wire MSD tach signal. The red with white stripe would be switched power and the the green I'm not sure? I don't want to guess on this.
    Last edited by 30rat; 12-20-2016 at 09:28 AM.

  5. #5
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    Well, I can't post anything even remotely negative, or they will delete it, but it sure sounds like you did not get the adapter that is listed in the Reference Manual. Was the adapter, HOLLEY part number 558-493?

  6. #6
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    Quote Originally Posted by 30rat View Post
    I don't want to guess on this.
    Contact Holley Tech Service (LINK) if you have further questions about the wiring instructions.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  7. #7

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    Quote Originally Posted by rel3rd View Post
    ...but it sure sounds like you did not get the adapter that is listed in the Reference Manual. Was the adapter, HOLLEY part number 558-493?
    Yes, that's the correct part number. I'm going to contact/call Holley Tech Support today and will post my results.

  8. #8

    Default

    Talked to Holley support this morning and they were very helpful.
    Plug Holley 558-493 Adapter Harness into distributor.
    Red/white stripe wire goes to a switched +12V.
    Green wire goes to chassis ground.
    Purple wire with small connector, goes to Sniper main harness purple/green wire small connector.
    I'll hook it up tonight after work and let everyone know how it went.

  9. #9
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    So you obtained the Holley 558-493 Adapter Harness, and received good Holley tech support. Sounds good to me.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  10. #10

    Default

    I finished the Holley Dual Sync Distributor install tonight, and here's my review:
    The Sniper EFI was a straightforward install other than upgrading the fuel system,
    which was just time consuming depending on which way you go with it.
    Night & day difference in throttle response & power with EFI. I give it an "A".
    The Holley Dual Sync Distributor is also a simple install, once you get the 558-493 Adapter Harness.
    Simply plug it into the ignition harness, purple to purple, green to green, red to switched +12V.
    If running an MSD box, plug in the 10-pin connector and connect the white wire to the MSD white wire.
    The 30_Rat (Instagram name) fired right up, and I can't wait to hit the strip with it. My grade is an A.

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