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Thread: Wire connections

  1. #1

    Default Wire connections

    My car is a '74 Corvette convertible with MSD Atomic EFI,
    - intank fuel pump (walbro 255LPH) with a return line
    - Aeromotive fuel pressure regulator A1000
    - MSD 8571 distributor incl MSD 84211 adjustable rotor
    - MSD 8207 Blaster SS coil
    - MSD 8,5 Super conductor wires
    - TH 400 transmission
    - 383 chevy stroker engine with hooker sidepipes (SS)

    1.) I not sure how I should connect the system – especially the white or yellow wire of the EFI.
    Should I connect the white wire with the gray wire of the MSD 6 ignition box, or should I take instead the yellow wire of the EFI...???

    2.) Is it important to use the yellow wire only if I'll make use of the timing control of the MSD Atomic EFI

    3.) Is it possible to use the orange wire to trigger a fuel pump relay...??? I'm not sure but I think the walbro needs permanet 12volts for working and the orange wire doesn't have permanet 12volts – is that correct...???


  2. #2

    Default Wire connections

    Are you trying to have the Atomic control timing? If not you do not use the adjustable rotor.

  3. #3

    Default Wire connections

    I used the Atomic timing control, Adjustable rotor and connected yellow wire of the EFI with the gray one of the MSD6A - and the car was running. But during the winter months I decided to control a few parts of the car. Stupidly I striped the complete electronic, headers, rear supsension etc..... While I was doing this I saw that the inside of the headers were not all black. Zyl.3 on Pessenger side and Zyl.2+4 on Driver side are white, looks like not used.

    That was the reason why I decided to control the whole system and why I scanned the MSD Installation Instructions again. There I found a picture where the WHITE wire is connected with the 6A, not the yellow one - like I did.

    Now I'm not sure what to do....



  4. #4

    Default Wire connections

    So it is white to the orange wire of the distributor and yellow to the white wire of the MSD box for timing control. Or white to the tach output of your dizzy if not using the atomic to control timing.

    If you swap to non atomic timing control, you need to unlock the distributor, add your advance weights back and remove the adjustable rotor.

    I'm not really sure why you would pull it all apart for this. I would have changed my spark plug wires and plugs perhaps but pulling all this apart is a bit much. Especially with side pipes, they are notorious for causing odd issues with the appearance of exhaust tubes. Oddities in reversion and random increase / decrease of scavenging ability changes the look of the tubes based on how you drove last.

    A thermal heat gun will tell you volumes as well even before shutting the engine off.

    For me, I would have

    1. Changed plugs

    2. Changed wires

    3. checked the heat at the exhaust port of each tube after a 15 minute drive and compared

    4. consider the intake as a possible issue as well. Runner length to each of the tubes that are white might be a bit longer and the AFR might be a bit higher. Increased AFR on the handheld would help to balance it a bit but inefficient intake flow cannot be cured with an TBI. You would need direct injection for this.

    I would bet prior to the TBI the tubes were black because every cylinder was running rich. Now two of them are lean.

    What exactly are you trying to do at this point? Remove the timing control? Or remove the Atomic?

  5. #5

    Default Wire connections

    The 8571 is a magnetic pickup, mechanical tach drive distributor.

    Please verify that the system is wired up as per Figure 19 on page 18 of the instructions (link below):

    The distributor to the throttle body, the Yellow wire of the throttle body to the White of the ignition box and the box to the coil.

  6. #6

    Default Wire connections

    I swaped the installation instructions on page 11 & 18 - I jumbled both.

    I did the installation like it is instructed on page 18 (fig.19) -

    Now I'll check a few other things fcsallan wrote (wires, puls etc...)

    Is it possible to trigger a relay for the fuel pump with the orange wire...??? I'm not sure if the orange wire is permanent 12Volt loaded ???



  7. #7

    Default Wire connections

    The voltage output on the orange wire depends on the fuel pump mode setting in the Atomic.

    Non-PWM runs the pump at a constant 12V as the system sees RPM.

    PWM sends pulses of 12V to the fuel pump to maintain a calculated pressure.

    The relay may be used in the Non-PWM setting.

    A relay is recommended with fuel pumps that will draw more than 20A.

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