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n12y vs. n9y champion spark plugs

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  • n12y vs. n9y champion spark plugs

    Hello
    Doing some basic tune up stuff to the tr6 and read that n12y plugs are a popular part. Shop manual recommends n9y plugs. After checking specs. noticed that the 12's were a hotter plug. O.k. to use the hotter 12 plugs? Using pertronix ignition w/flame thrower coil also bypassed ballast resister per Dan Master's suggestion.

    Thanks

  • #2
    May have to do more with your compression ratio. The higher the ratio the need for a hotter plug.

    Comment


    • #3
      The short answer is both can work. The long answer is according to Champion, for normally aspirated, gasoline-fueled engines, a good rule of thumb is to go about one heat range colder for each full point in compression ratio increase from 9:1 through about 12.5:1. Our cars are below 9:1 so that's not an issue. The air fuel ratio, amount of timing advance and engine load also come into play. If your engine runs closer to AFR 14:1, under load, a 12 might be too hot. If you drive sustained hard or run a lot of timing, a 12 might be too hot.

      My car came with 9's and I run them with good color the way it's driven and tuned.

      Greg

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      • #4
        Fue/air mixture and ignition timing are big factors along with how and where you drive.
        9's don't last too long without fouling in my engine except for sustained highway driving.
        12's (or should I say plugs in the 12's heat range) burn cleaner for the way my engine is tuned and the way I drive.
        Experiment..see what plugs and gaps your engine prefers with the way you drive and how you have your engine tuned and timed would be my advice...
        Driving a 1973 TR6
        Doing ZS carb repairs
        email kencorsaw"at"aol.com

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        • #5
          When I got my first '250 in '76 the stores all showed N9Y as correct for TR6. These were not correct for '250s or early TR6s and fouled in short order in mine. Then I saw " UN12Y " in the owner's manual. The hotter plugs didn't foul, and I stayed with that heat range until 20 years later when they ran white in my Webered, souped-up engine. I've been with the N9Y range ever since.

          I heard the later TR6 low compression, super lean tuned carbs took the cooler plug. I suspect many of these have lost their " tune " and run a bit richer, so will benefit from the hotter plug.

          My brand preference since the 1900s has been NGK; when I first switched the N9Y correlated to BP7ES and the N12Y to BP6ES. Mine get changed every 30,000 miles whether they need it or not, and I gap them to 0.030" instead of 0.025". LUCAS Sport coil and Standard points.


          Tom

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          • #6
            So you run the cooler plug in your TR5 spec w/Webers, Tom?

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            • #7
              So you run the cooler plug in your TR5 spec w/Webers, Tom?
              I do, and they also run fine in my other engine with higher c/r and higher lift / longer duration cam.

              NGK BP7ES - I think this is the most popular plug with the UK specialists for the TR5/6 application.

              Tom

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              • #8
                My 71 came with Champion RN12YCs' in it 5 years ago, and I have not bothered to change them. They run fine, don't seem to foul up appreciably in traffic, and colour of tips appears to be in the desired range.

                However, due to some impending engine modifications, I was wondering about plug choices to suit. Came across this article on the NGK Website which I thought did a good job of explaining what are the considerations behind plug heat ranges.

                Spark Plug Basics

                FWIW - Based on what I have read, and advice from various respected sources, I plan on experimenting with a cooler plug
                Keith, Huntsville AL, 1971 CC66559U
                10.0:1 CR gasflowed head | Weber DCOEs | CP "150hp" Cam | Good Parts Ram-Air induction | Distibutor by Advanced | Lightened flywheel | Phoenix SS Exhaust System | HVDA 5-Speed | Good Parts R200B Diff and CV axles | Good Parts suspension and anti-roll bars | Willwood Calipers and Vented Rotors | Good Parts Dual Brake Master Cylinder | Konig Rewinds | Boyd 15 gal tank | Miata Seats and Mr Mikes covers | Carl Visser dash | Mohair hood | Gas-strut bonnet and boot lift kits

                Comment


                • #9
                  Thanks for that article, Keith. Didn't know about insulator length's effect on heat range.

                  Notably, many P.I. engines are happier with the hotter plug. However, the cooler one is specified in the literature.

                  Overall, I reckon the hotter one is likely suited to the vast majority of the TR6 engines.

                  Not a big risk to try the hotter one; it won't foul and unless it runs white keep it.

                  Tom

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                  • #10
                    Thanks, Tom. Reason I asked for clarification was that I was reading Roger William's book the other night, How to Improve TR5, 250 and 6, and in that he recommended a hotter ignition for Webers on the 6. He's not shy about trashing the whole notion of putting Webers on the 6, except for dedicated racing applications, which led me to do a double take when you recommended a cooler spark, but hey, you have the miles to show it works!

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                    • #11
                      I haven't read Roger's book :unsure:

                      - and I certainly don't plan to now! :P

                      As I've said on other occasions, if TRIUMPH had fitted DCOEs to the 5 and 6 they'd probably be worth 2x ( TR6 ) or 3x ( TR5 due to rarity ) today. With the passage of time I am more and more convinced of it.

                      Performance, reliability, precision control of A/F ratio ( clean burning! ) and...vintage cachet!

                      Tom

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                      • #12
                        Thanks for the info. guys, as always very informative

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                        • #13
                          Don't think that the Champion (R)N12yc 's are the hottest plug in the line up; they are just the hottest Champion plug that's normally used in our engine..
                          Champion has automotive spark plugs going up as high as 25 in the heat range. It's all relative.
                          Driving a 1973 TR6
                          Doing ZS carb repairs
                          email kencorsaw"at"aol.com

                          Comment


                          • #14
                            Hot engine, cold plugs.....and vice versa

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                            • #15
                              My humble experience has shown that the NGK plugs are capable of running a wider heat range than the Champions. i.e. a BP6E will cover two of the listed Champion plug heat ranges. Plus, in my experience, they are less susceptible to fouling( but that is a big factor of fuels used).

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