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Spark Plugs??????

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  • patrick santaniello

    Spark Plugs??????

    I was thinking of going to nonresitor pulgs in my l71 motor.Is that going to help in any gains in perforamce or am i wasting my tme.If it is a good idea were can i get 43N plugs.Will i have to change them more often? Most of my drving is stop and go with a few long rides to ncrs meets and bloomington gold.Thank you for your time.
  • Dave S.
    Extremely Frequent Poster
    • August 31, 1992
    • 2918

    #2
    Re: Spark Plugs??????

    Are you currently running R43N plugs or a higher heat range like 44 or 45? I have found 43 plugs in a big block are too cold(especially for city use)and a heat range of 45 is best for all around driving. I'm not sure you can tell the difference in performance between resistor and non resistor plugs.

    Comment

    • grr

      #3
      Re: Spark Plugs??????

      I use Splitfire Plugs in my 67 L-71,MFR.# SF40D,gap .035". No problems.grr.#33570

      Comment

      • patrick santaniello

        #4
        Re: Spark Plugs??????

        Thank you dave.Does your engine run any hotter with a 45 plug.

        Comment

        • motorman

          #5
          Re: Spark Plugs??????

          there are no performance advantage to non resistor plugs,even F-1,and indy race cars use resistor plugs because of the interference that non resistor plugs would cause with the electronics on the cars.

          Comment

          • Dave S.
            Extremely Frequent Poster
            • August 31, 1992
            • 2918

            #6
            Re: Spark Plugs??????

            Patrick, No noticeable difference in engine temperature with the hotter plug.

            Comment

            • Dale Pearman

              #7
              Re: Spark Plugs??????

              Resistor spark plugs ain't got a resistor in them! They have a DIODE which breaks down with reverse voltage for each spark. This causes the rise time of the spark pulse to improve dramatically. A carbon fouled plug presents an inductive path to current. Therefore a slow rising pulse would simply bleed through the resistive carbon path without jumping the gap. PRESTO-MISFIRE! If a real high pulse happens all at once (short rise time), the current will jump the gap instead of bleeding through the carbon deposits. There isn't enough time available for the current to overcome the inductance of the carbon.

              Therefore the so-called resistor plug is really a semi-conducting pulse shaper device using a diode to improve rise time and very useful in firing carbon fouling engines.

              The same thing can be accomplished with a pressure depleted tin can and two electrodes spaced apart by say 0.050 inch. The voltage increases across the gap in the can until current jumps instantaneously and a very short rise time spark is presented to the plug which will fire even if fouled. This MIRACLE device is promoted by hucksters at carnivals and swap meets for about $39.95 with an unconditional guarantee. It really works! Impressive demonstrations are provided. "Resistor" plugs do the same thing a lot cheaper!

              While on the subject, a LONG duration spark, such as that provided by GM's HEI is the way to go. If the fire burns a long time, the chances of a hydrocarbon molecule drifting into the flame is greater than with a short duration spark. Capacitive discharge systems have a VERY short rise time AND a very short duration. The short rise time is an asset BUT the short duration is a liability. The spark may "cavitate" through the fuel-air mix and miss a molecule causing a misfire. The successful capacitive discharge systems of today use a succession of short duration sparks depending on RPM. (MSD) They seem to work pretty well.

              In summary, the "resistor" plug is helpful in any ignition system due to pulse shaping action. You can time the spark much more accurately and expect the setting to remain stable even in the face of one or more plugs tending to foul. In an engine WITHOUT fouling problems, NO performance improvement will be noted. In other words, "It can't hurt and maybe it will help"!

              Rev. Varooom!

              Comment

              • patrick santaniello

                #8
                Re: Spark Plugs??????

                Thanks to everyone that posted a response.I still dont know what to do?Maybe go to a hotter plug .maybe a 45 like dave said to see what it does.Thank you,have a nice summer.......

                Comment

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