360 Spark Plug Gap | FerrariChat

360 Spark Plug Gap

Discussion in 'Technical Q&A' started by Kevin Rev'n, Jul 21, 2020.

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  1. Kevin Rev'n

    Kevin Rev'n Two Time F1 World Champ
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    Nov 29, 2009
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    #1 Kevin Rev'n, Jul 21, 2020
    I see that the manual shows a pretty big range of tolerance for the gap. I am changing mine out and the new NGK PMR8B plugs come out of the box at .024" but the ones i am pulling out of my car are at .028". My car runs so good I was planning on opening the new ones up but I thought maybe I could learn something if I post a thread about it. Is there anything I should know before I do this?
    from the manual...
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    What my 16k miles plugs look like (#1)

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  2. Tegethoff

    Tegethoff Formula Junior

    Jul 19, 2014
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    #2 Tegethoff, Jul 21, 2020
    As long as the rest of your ignition system is functioning properly and capable of generating enough voltage to bridge the gap, larger gaps are preferable.

    0.028”/0.70mm should be fine.

    If you do see any missing, power loss, or idle instability, they can be closed back up to the lower side until you locate the next weak link in the ignition system. Given that you currently have 0.028 I doubt you will have an issue.

    Was .028 what you set them at the last time they were swapped, or what you currently measure? I only ask as the gap opens over time due to material vaporization. IE: set plugs at .024, x0,000 miles later they are at .028
     
  3. Kevin Rev'n

    Kevin Rev'n Two Time F1 World Champ
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    #3 Kevin Rev'n, Jul 21, 2020
    Thanks for the reply, I have only had the car since 2013 but I got it with 5,600 miles on it. Now ~16K miles, so the plugs may be original although I need to see what year the NGK spec changed from PMR8A to PMR8B to be sure. Do you think that the gap could have widened from 16K miles? The spec for replacement is 30K miles. Car is a perfect specimen no odd running or power loss.
     
  4. Tegethoff

    Tegethoff Formula Junior

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    #4 Tegethoff, Jul 21, 2020
    Wear on iridium's is pretty good, but 11/16k is a decent amount, from your pic is does look like the tip is ever so slightly shorter.
     
  5. Kevin Rev'n

    Kevin Rev'n Two Time F1 World Champ
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    #5 Kevin Rev'n, Jul 21, 2020
    I went more carefully over the new plugs and they are closer to .025 than .024 so I am going to install as is.

    Now I need to decide whether to use Anti Seize or not! lol
     
  6. tazandjan

    tazandjan Three Time F1 World Champ
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    Terry H Phillips
    #6 tazandjan, Jul 21, 2020
    NGK puts a special plating on the plugs and specifically says not to use anti-seize when installing. It also can lead to over-torqueing the plugs since it acts as a lubricant.
     
    Texas Forever and Kevin Rev'n like this.

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