1970 340 SPARK PLUG RECOMMENDATIONS

Small Block Mopar Engine

  1. raydurr

    raydurr Active Member

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    Hello. I have begun the tuning process of my 340. It has a mild hyd. roller. ,headers and MSD.
    I currently run stock replacement Champions. What manufacturer and what PN do you guys run?
     
  2. SGBARRACUDA

    SGBARRACUDA ROY FABO Gold Member

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    In my 70 340 4 speed Duster I ran N-9y Champions and never had a problem. Thou some will not agree. Just watch.
     
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    • MOPAROFFICIAL

      MOPAROFFICIAL Well-Known Member

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      I make my own.
      Good luck.
       
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      • SGBARRACUDA

        SGBARRACUDA ROY FABO Gold Member

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        Spark plugs?
         
      • SGBARRACUDA

        SGBARRACUDA ROY FABO Gold Member

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        I ran J-8 in my 440 bracket car. They lasted for ever.
         
      • brian6pac

        brian6pac Well-Known Member

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        N9Y or Autolite 63 worked for me, I got more mileage out of the Autolite's.
         
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        • RustyRatRod

          RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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          Stock replacement Champions.
           
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          • SGBARRACUDA

            SGBARRACUDA ROY FABO Gold Member

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            That's right I forgot about the Autolite 63's I used them also with good luck.
             
          • MOPAROFFICIAL

            MOPAROFFICIAL Well-Known Member

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            Lol yeah, Coat hangers and hollowed rtv filled bolts... kidding..i meant it like.. 'ah ha, take that' to those brand pushers. If I was a moderator on here I'd probably just delete every single one of these.. "what oil should I use?" ..."what spark plug should I use?"...threads and just make a sticky that says ..to use high zinc content for flat tappet cams and to use a spark plug that you can easily read and is the correct heat range ...and call it good.
             
            Last edited: Jun 28, 2019
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            • harrisonm

              harrisonm Well-Known Member

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              Here we go again.
               
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              • ch1ll

                ch1ll FABO Gold Member FABO Gold Member

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                Champion still makes a n9y?

                I had a set of accel plugs that ran good.

                Any of you folks experience the last few years of leaded gas, seems to me plugs didn’t last all that long.
                 
              • Oldmanmopar

                Oldmanmopar Going left turning right FABO Gold Member

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                In 1984 I had a 69 340 swinger for a work car . I bought a 318 car to part out and there was a set of new N12y's in the box on the seat. I thought great a free tune up. I came home from work and put the used N9y's back in the next day and tossed the 12's. Probably would be different with todays fuel. I would say install a set and read them.

                in the 80's I would drive the car get it hot. pull over on a long straight and install one plug. Have one plug of various heat ranges with you. Start the car and do a 1/4 mile run. shut the car off coast to the side pull the plug and read the strap. If its burned back past the bend go colder and try again. Every motor likes a different plug depending on fuel and motor build. Most 340's did like N9's or 63's. These new High energy ignitions with multiple spark and todays fuel changed most needed heat ranges for many motors. You cannot go by those old books anymore except to get close to what you need.

                You could take it to a Dyno shop and pay them to do it for you. $$$
                 
              • raydurr

                raydurr Active Member

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                The reason that I asked is I have done tune ups in the last few years with Champions and had issues. I know they were 1st choice decades ago but have they changed?? It seems like Autolites work well in everything I use them in.
                 
              • yellow rose

                yellow rose Overnight Sensation FABO Gold Member

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                Pump gas and under 11:1 you'll need the RC12YC champion.

                There is a reason the Champions don't last as long. It makes sense if you know why that is. Expecting a set of plugs in a performance engine to go more than 10k is silly. Plugs are cheap. Replace them every 5k and the tune up is better.
                 
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                • Wyrmrider

                  Wyrmrider Well-Known Member

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                  Is this a high or low compression 340?
                   
                • rumblefish360

                  rumblefish360 So close, yet so far away FABO Gold Member

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                  Man! Hammer on the nail head! They go a good bit longer in the more stock engined rides.
                   
                • SGBARRACUDA

                  SGBARRACUDA ROY FABO Gold Member

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                  Most headaches today are from Ethanol gas. Since I switched the Dart and Barracuda to non ethanol, my life has become much easier. On the Barracuda with 10.7 CR, I add octane booster.
                   
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                  • 69_340_GTS

                    69_340_GTS Well-Known Member

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                    Back in the '60s-'70s you'd be lucky to get 6,000 miles out of a set of plugs. I don't think it is much different today (with old engines) no matter what fuel you're using. It's just the way it is.
                     
                  • Wyrmrider

                    Wyrmrider Well-Known Member

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                    still do not know the compression ratio or cranking compression
                    makes a big difference in plug selection
                    any idea what heads and pistons U have?
                     
                  • ocdart

                    ocdart Inland Mopars Car Club FABO Gold Member

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                    I couldn't get Champions to last on my '69 Swinger 340 back then. I always had good luck with Autolites performance and lifetime. Of course, back then I changed plugs a minimum of twice a year.
                     
                  • Johnny Dart

                    Johnny Dart Well-Known Member

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                    NGK and then Autolites in that order.
                    Find the proper heat range, and go.
                    Champions in the lawnmower.
                     
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                    • George Jets

                      George Jets 1967 Dart 2 Door FABO Gold Member

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                      Just for the fun of it I "Sonic Cleaned" some old Champion RN12YC from back in the day, they cleaned up like new.

                      Have been running them in my stock 360 4 bbl. They are working great and burning nice and clean.

                      Pictured below are the plugs, this was after a pretty good run with non ethanol fuel in the tank.

                      20190615_204332.jpg

                      20190615_202629.jpg

                      Fun to put them back into service . . .
                       
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                      • Wyrmrider

                        Wyrmrider Well-Known Member

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                        we don't yet know the compression but that extended tip is going to work better in a low compression 340 also
                        also check out RFN14LY and similar styles for low compression there is/was a colder version available
                         
                      • MOPAROFFICIAL

                        MOPAROFFICIAL Well-Known Member

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                        For those reading that..
                        longer tip...hotter plug.
                        Shorter tip...colder plug.

                        Too hot a plug range and you'll create potential for preignition.
                        Too cold and you'll fool the plug =blackening of the insulator.
                         
                      • yellow rose

                        yellow rose Overnight Sensation FABO Gold Member

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                        Can't see much, but the timing looks close and the cruise and idle circuits are pretty damn spanky. I'd like to see a better shot of the ground wire and a picture of the insulator with the shell off.
                         
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