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Thread: Plug Gap - Best Guess

  1. 06-30-2012, 10:33 AM #1
    luke-44
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    Plug Gap - Best Guess

    I am replacing the plugs on 301596 - I'm new to the car so don't have much to go on. Records from the car indicate it had a "2.2S" kit installed at the last engine rebuild. Car is running webers (I'm rebuilding those right now too), not the Solex's if that matters.

    The plugs that came out of the car were Bosche W7DCO. Typical gap of the old plugs was +-.035". The plugs were quite sooty. The new plugs comes pre gapped to .032". Factory owners manual suggests Bosche W 250 P 21 with a .014" gap. How far apart in heat range are these 2 plugs? At this point I am just replacing the existing plugs in kind until I can get some experience and then tweak from there.

    Any suggestions where I should set the gap to start with on the new (W7DCO) plugs? Thanks in advance,

    Last edited by luke-44; 06-30-2012 at 10:35 AM.
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  2. 06-30-2012, 11:24 AM #2
    edmayo
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    What ignition system are you running? Stock or C.D. (as would have been on a 2.2S) If stock then follow the specs you have, if C.D. they called for .024" A 250-p21 is colder than a W7 series. In NEW Bosch system lower number equals colder, just opposite of their old system, I think the change occurred sometime back in the eighties. Just for reference back in the day, a 265-p21 was for an S, and the 250-p21 was for the E. Just to further muddy the waters do NOT use the new style platinum with the center electrode imbedded in the porcelain, they seem to work best with newer lean burn engines. I prefer the NGK BP7ES for early type engines. That is what i run in my early S's.
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  3. 06-30-2012, 01:16 PM #3
    luke-44
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    Quote Originally Posted by edmayo View Post
    What ignition system are you running? ..If stock then follow the specs you have, ...
    Stock ignition. So to clarify, are you saying gap them to .014"? Seems so small.
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  4. 06-30-2012, 07:12 PM #4
    edmayo
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    I agree it was certainly smaller than we are used to seeing. I can't honestly say what gaps we were using back in the sixties and seventies when these cars were most current, but I do know that nowadays I set the gaps to .024" I'm sure the engineers were trying to insure there would always be enough voltage from the coil to jump the gap. Of course the biggest change since then is unleaded gas, less deposits build up. Use the .024"
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  5. 07-01-2012, 07:28 AM #5
    luke-44
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    Thanks Ed. .024" it is.
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