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Old 07-30-2006, 08:49:23 AM   #1
andymiller
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Spark Plug gap for MSD box

What spark plug gaps are you guys using with MSD boxes? I have a mild built 355 and running a MSD 6a box. Basically a stock type HEI dist. 9.6 cr
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Old 07-30-2006, 09:20:14 AM   #2
CorkyE
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I've been up and down the range of gaps and found .040 works best for me. Really, you'll just have to play around, but .040 will be a good starting point.
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Old 07-30-2006, 09:54:47 AM   #3
Damon
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.045 is about where I run them. You can probably go wider but I never do on a street motor- the wider the gap the more strain it puts on the whole secondary side of the ignition. My brother runs them at .065 but he always seems to be replacing coils and coil wires a lot more than me. I usually go years without wearing out ignition components.
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Old 07-30-2006, 08:48:08 PM   #4
Joekool
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With 9.6 to 1 c/r .040 to .045 should be fine, if your compression where to increase then you would need to lower the plug gap. I have around 10.25 to 1 and .035 seems to work the best for my engine.
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Old 07-31-2006, 06:02:35 AM   #5
andymiller
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I've always heard you wanted tp run a large gap with these things to make a big hot spark.
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Old 07-31-2006, 08:19:40 AM   #6
Marv D
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The larger the spark kernel the better, but when you start running more and more compression it is harder for the electricity to jump the gap, so you have to give up a large spark for reliability of the plug firing every time. At 14:1 you'll typically see the racing plugs gapped at around .028 -.32. But like Damon suggested, MSD suggests a starting point around .035-.045 for normal street compressions.
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Old 07-31-2006, 12:39:46 PM   #7
blue 79 Z28
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Quote:
Originally Posted by Marv D
The larger the spark kernel the better, but when you start running more and more compression it is harder for the electricity to jump the gap, so you have to give up a large spark for reliability of the plug firing every time. At 14:1 you'll typically see the racing plugs gapped at around .028 -.32. But like Damon suggested, MSD suggests a starting point around .035-.045 for normal street compressions.
i agree. for n/a i run .035 on mine, and for nitrous i run .030 thats with a digital 6 ignition, and just over 11:1 on the motor, never had a plug issue or ignition hiccup.
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