Heat Range Experts: What plug to use?

Electrical and Ignition

  1. OlDuster

    OlDuster Well-Known Member

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    I know the 'manual' lists a N13Y for the 8.6 360 and a N9Y for the 10.5 340. When we machine and rebuild these engines, what plug range should I use? I have a 9.5 340 and a 9.4 360. My 360 is missing occasionally and I am running the N9Y Champions. I think they are too cold a range for the 9.4 compression. I am using a Bosch Platinum plug in my 340 and it runs fine. It is the same "range" as the N9Y. What plug should I put in my new 360. I have about 150 miles on it and will start to work it a bit, soon. I am wondering if a N10Y would warm it up a little and stop the fouling. N12Y? What do you guys run on these street motors?
     
  2. EvilScamp

    EvilScamp Well-Known Member

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    I'm running N12Y Champion in my 340.They work fine for me never had any problems with them.
     
  3. six pack

    six pack Well-Known Member

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    See if you can find some RN11YC's but do not use a bosch platinum, these are junk in a Mopar. I have removed too many sets for customer that came in with misfires.
     
  4. OlDuster

    OlDuster Well-Known Member

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    EvilScamp: What is your 340's compression ratio with the N12Y? I am thinking that a set of those will work in my 9.4 360.

    SixPack: What about the RN11YC plug in the 340? What compression ratio are you putting these plugs into. Maybe I should try that in my 9.5 340 instead of the Bosch Platinum plugs.
     
  5. six pack

    six pack Well-Known Member

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    I know the heat range was 10 for most of theMopar muscle cars that were over 10:1 compression.
    RN11YC were used in the mitsu 3.0L engine that had 150-160 psi cylinder pressure so I would think they would probably work well for your application.
     
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