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Thread: How do I dail in spark plug gap?

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  1. #1
    BigTruckDriver is offline CHR Member/Contributor Visit my Photo Gallery
    Join Date
    Dec 2004
    Car Year, Make, Model: hotrod

    How do I dail in spark plug gap?


    I have a 89 350 TBI and have upgraded the ignition. Now, stock calls for the plugs to be gapped at .35. I am finding that just with a MSD coil people are gapping up to .55. How do I know where I need to be? Do I just start opening up the gap until power starts to drop off? This is not a high performance motor but I am building up performance for increased fuel economy. Thanks
    Friends dont let friends drive fords!

  2. #2
    WRENCHD is offline CHR Member Visit my Photo Gallery
    Join Date
    Dec 2005
    north west
    Car Year, Make, Model: 64 DODGE 440

    hey big
    well if you up graded the ign then i would assume that the coil is also up graded?
    hei mostly starts at 45 for the gap and goes wider from there, i've set mine to 45 and didn't have any prolems at all from idle to wot. if you are looking for fuel econ, then leave it at 45 and set the timming to spec's for the engine. depending on how high you are from sea level you could bump the timming up 2 to 4 degrees to get max power and fuel. the other thing imo is that you should use autolite plugs. if you want to get more involved then you can (very carfully) work the two screws on top of the fuel injectors and adjust the fuel delivery, it's kind of touchy to do but you might get alittle out of them. kee th oil and the filters clean and enjoy.

  3. #3
    460motorvator is offline CHR Member Visit my Photo Gallery
    Join Date
    Nov 2007
    Car Year, Make, Model: 1961 fairlane 2door hardtop

    bigger the gap,less responce off idle,up to you?

  4. #4
    markw is offline CHR Member Visit my Photo Gallery
    Join Date
    Jun 2007

    I'm running an MSD 6AL box and it would probably fire a .09 gap but the cap and rotor wouldn't last a week. I haven't seen any improvement running over .045 gap. It just tears up the wires and cap and rotor. If your mixture is right and your not burning oil .035 to .045 should fire any motor just fine.

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