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Old 09-29-2004, 11:43 AM
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Sparkplug wire resistance

How can you tell if plug wires wires are marginally bad, and how do they fail.

I have a 350 SBC, MSD6AL with Taylor wires, MSD distributor, ( New cap and rotor). I recently re-crimped ends on to the wires, and have a few wires with 3x as much resistance as the others.

The engine misses over 4000 rpm, I have replace the cam, plugs, adjusted the valves and in general am running out of clues. By the way, carb is a Barry Grant 850, bigger than I would like, but I don't thinks this is the cause of my high rpm miss.

Is there an acceptable range of resistance for "Good" wires?

Thanks for the help

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Old 09-29-2004, 12:02 PM
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Rule of thumb is 1000 to 4000 ohms per foot of wire.
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Old 09-29-2004, 12:09 PM
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that would explain why my ohm meter always measured infinity. never could figure that out. guess i shouldnt be measuring with a digital multi meter.
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Old 09-29-2004, 01:37 PM
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The better made wire is 100 or less, the new Moroso is 40 OHM per ft. , is the best on the market today. Good Mallory wires are 50 OHMs. You will not get a reading if the wire is burnt.
The lower the OHM the hotter the spark.
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Old 09-29-2004, 01:57 PM
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The msd wires I just bought are 40 ohms per foot. bm
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Old 09-29-2004, 05:44 PM
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Ah the ol' superconductors. Just did am ohms test on them after running under the hood of a Vette (and it gets hot under there) for 1.5 years. All within 40-50 ohms (per foot).
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Old 09-29-2004, 06:00 PM
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Yep, MSD 8.5mm super wires are 40 per foot.

Vince
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Old 09-29-2004, 07:05 PM
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I measure with an Ohm meter and I also do a "fourth of July" test as well: spray the engine (leads) with water, shut off the lights, and start the engine. If you see fireworks like the Fourth of July, you need new leads.
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Old 09-29-2004, 11:13 PM
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I think the 4000-5000 ohms/foot figure refers only to carbon-core resistor wires.
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Old 09-30-2004, 07:13 AM
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Smile

Thanks for the help, I believe new wires are in order.

Regards

VegaHigh
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Old 09-30-2004, 10:40 PM
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went out and checked the ones on my car 7000 ohms per foot

owch, time for an upgrade
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