Spark Plug Help

1971 - 1974 Mopars

  1. ODZKing

    ODZKing Well-Known Member

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    I posted over at DC.com as well and seems no one has an answer.
    Back when we did the 73 engine, in checking on plugs for the 400 4bbl, I came up with the original # of J11Y. I crossed it (then) to RJ14YC. I am about to get a new set and to my surprise, what is recommended RJ12YC which is the same plugs as my 67 - 383 4bbl.
    http://www.sparkplug-crossreference.com/convert/CHAMP_PN/J11Y
    So researching as I do, I realized the RJ14 is a bit longer. Not being a genius when it comes to this I have to question ... what is the difference between the two lengths and have I been using the WRONG plugs in my 73 400 4bbl all this time?
     
  2. moparnation74

    moparnation74 FBBO Gold Member FBBO Gold Member

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    Dc.com....rather quite over there these days:realcrazy:.....

    RJ12YC(colder) this is the correct plug for your 400....the reach is .380"

    RJ14YC is .375"...Difference is this one is a hotter plug...

    IMHO the newer Champions are junk and if you want to run champions then pay up for an NOS set of J11's. The old plugs are a night and day difference in quality, longevity and performance....

    If you want the cheaper priced new plugs the first choice is Autolite 85's or NGK's.....
     
    Last edited: Jun 19, 2017
  3. Nacho-RT74

    Nacho-RT74 Well-Known Member

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    Weird I didn't reply there since in my Mopar Boards routine DC.com is my first board to visit. Simply I just missed.

    I always have got locally J12Y because were the only ones available locally and used with success. Haynes manual says RJ12YC for 70s HiPo big blocks

    When i got my Credit card and was abl to import parts from USA, got around two sets of RJ12YC, then changed to NGK per advises, XR5's which are V groove.
     
    Last edited: Jun 19, 2017
  4. lewtot184

    lewtot184 FBBO Gold Member FBBO Gold Member

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    with champion plugs the higher the number the hotter the plug. j11y's and j13y's were designed for the mopar head. the projected tip on these two plugs is a little longer than j10y's and j12y's. the j11y and j13y plugs are extinct. the j12y will work. an autolite 85 will work well too. the original plugs were non-resistor. the j12y and autolite 85 are resistor.
     
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    • ODZKing

      ODZKing Well-Known Member

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      So if I go with NGK's, 400 = XR5.
      How about 383 4 bbl also, which NGK for that engine?
      In looking at Rock Auto, they recommend XR4's for the 383.
       
    • moparnation74

      moparnation74 FBBO Gold Member FBBO Gold Member

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      XR5's for both.....

      XR's are recommended by the general search feature because 383 is a lower compression motor but it doesn't account for your needs...
       
    • ODZKing

      ODZKing Well-Known Member

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      OK, same price as Champions so I will give them a shot.
      BTW, if anyone is looking, $1.38 at Rock Auto, cheapest I can find. $5.99 shipped to me for 16 (2 sets). $28 and change, is still cheaper than I can get them locally.
       
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      • moparnation74

        moparnation74 FBBO Gold Member FBBO Gold Member

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        It will be 28 bucks well spent...
         
      • Nacho-RT74

        Nacho-RT74 Well-Known Member

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        Plus 5% on discount code
         
      • ODZKing

        ODZKing Well-Known Member

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        Huh, what discount code ... too late, ordered them today.
         
      • Nacho-RT74

        Nacho-RT74 Well-Known Member

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        They allways have a discount code ( 5% tipical )... is just about search it. I even have googled to find it, but lot of ppl uses to post them on the boards ;)


        I have got it emailed sometimes
         
      • Nacho-RT74

        Nacho-RT74 Well-Known Member

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