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Jocko_51_B3B

Non-Resistor Spark Plugs

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Will non-resistor spark plugs improve spark (and therefore performance) in our 218 flatheads? Is there a downside to resistive plugs?

Edited by Jocko_51_B3B

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On 8/4/2018 at 5:47 PM, Jocko_51_B3B said:

Will non-resistor spark plugs improve spark (and therefore performance) in our 218 flatheads? Is there a downside to resistive plugs?

its my understanding that the resistor only pulls out electrical interference. As these motors have rudimentary electrical systems, I don't think it would make a difference either way. (using resistive or non resistive)

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well, as I recall from looking at the O'scope on Mopar ignitions years ago,  there is a difference, but I doubt there is any perceptible performance change.

 

The coil output will only rise until there is enough energy to jump the plug gap.  At the same gap, a resistor plug will offer more total resistance and the voltage will rise further as a result, to the coils' limit of course..  You can see it on a scope, but I can't feel it when driving.   It may help prevent misfires in some conditions, I don't know for sure.

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8 hours ago, kencombs said:

well, as I recall from looking at the O'scope on Mopar ignitions years ago,  there is a difference, but I doubt there is any perceptible performance change.

 

The coil output will only rise until there is enough energy to jump the plug gap.  At the same gap, a resistor plug will offer more total resistance and the voltage will rise further as a result, to the coils' limit of course..  You can see it on a scope, but I can't feel it when driving.   It may help prevent misfires in some conditions, I don't know for sure.

 

 

 

You are probably right( I haven’t compared the two on a scope), but the manufacturers insist there is no difference or performance advantage of one over the other(besides the resistance).  I remember a lot of people used to say resistor plugs didn’t work as well in snowmobiles.  NGK and Champion said that simply isn’t true.  I’ve been in the parts business for over 20 years and the manufacturing companies have spent a lot of time and money telling us that.  😆😆😆

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FWIW NGK BR6S plugs work extremely well in these engines. Been using them for about 3 years now in my daily driver. They simply run cleaner than the rest of the plugs I tried early on. I think the heat range is dead on for this engine. NGK seems to have a better handle on this very important aspect than many of the other guys. At least that has been my experience for many years and many different applications.

Jeff

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1 hour ago, greg g said:

Aren't we instructed to gap resistor plugs at 30 thousandths as compared to 25 for non resistor?

With all the different possibilities for ignition systems these days, stock, 'hot' coils, 12v conversion with/without  resistor, 70s Mopar electronic, with/mopar/gm module etc, I'm not sure anybody follows the instructions on gap.   Somewhere between .025 and .080 can/will work with all the choices!

 

But, I think you're right when dealing with a stocker.

Edited by kencombs

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