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Old 01-07-2013, 01:26 PM   #1
model A hooligan
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Default spark plug wire ohms

So after sitting a month my sbc powered hotrod has a dead cylinder.it has HEI and I testedbthe ohms of the wires only 2 was bellow 11, 000..I had to as high as 16, 000.

What's the limit here?
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Old 01-07-2013, 01:30 PM   #2
325w
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Default Re: spark plug wire ohms

I stuffed some HEI wires in an original style early GM wire holders. Ended up cutting the wire and breaking it down eternally. Caused the plugs to fail to fire.
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Old 01-07-2013, 01:32 PM   #3
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Default Re: spark plug wire ohms

Most good plug wires are around 500 Ω per foot - do the math for your length

EDIT: A little quick checking on an old Motors manual and I see that 3,000Ω per foot was not uncommon for stock wires back in the 60's and 70's. I think you can run up to 20,000 Ω and it will still run OK, not as efficient as say 1000Ω but no problems either if the rest of the ignition system is up to snuff
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Old 01-07-2013, 01:33 PM   #4
model A hooligan
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Default Re: spark plug wire ohms

Well mine arnt in holder's.I'm just asking if these numbers are really high.I though anything over 11, 000 was high but I want to confirm that.

BUT one of mine burned pretty bad on my lake header.it ran fine before line that but maybe the cold helped ruin it
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Old 01-07-2013, 01:34 PM   #5
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Default Re: spark plug wire ohms

1000 ohms per foot is the general rule for most plug wires, unless you use Moroso, MSD, etc that are rated at 40-50 ohms per foot.
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Old 01-07-2013, 01:34 PM   #6
model A hooligan
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Default Re: spark plug wire ohms

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Originally Posted by hotroddon View Post
Most good plug wires are around 500 Ω per foot - do the math for your length
By that formula mine are hardly able to pass as a wet stick!
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Last edited by model A hooligan; 01-07-2013 at 01:39 PM.
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Old 01-07-2013, 01:40 PM   #7
model A hooligan
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Default Re: spark plug wire ohms

Alright I guess these are really bad then.I'm debating on getting the Taylor's at summit or just some regular ones since I seem to burn them once a year
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Old 01-07-2013, 01:49 PM   #8
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Default Re: spark plug wire ohms

If you burned them there is a good chance that they are "leaking" - letting the spark jump somewhere to ground instead of firing the plug. Path of least resistance and all that.
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Old 01-07-2013, 02:26 PM   #9
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Default Re: spark plug wire ohms

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Originally Posted by hotroddon View Post
If you burned them there is a good chance that they are "leaking" - letting the spark jump somewhere to ground instead of firing the plug. Path of least resistance and all that.
Yea, a plug wire can check out well OHMs wise and still be leaking like a sieve.

ModelAhooligan. Get that sucker in the dark and light it iff now look for sparks.
Anther thing you can do it lift the wires one by one while it is running so that they are not touching anything and see if the miss goes away. Sometimes it is best to use a pencil instead of your hand for this procedure.
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Old 01-07-2013, 03:49 PM   #10
model A hooligan
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Default Re: spark plug wire ohms

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Yea, a plug wire can check out well OHMs wise and still be leaking like a sieve.

ModelAhooligan. Get that sucker in the dark and light it iff now look for sparks.
Anther thing you can do it lift the wires one by one while it is running so that they are not touching anything and see if the miss goes away. Sometimes it is best to use a pencil instead of your hand for this procedure.

Haha I was messing with it the other day and got shocked.my magneto go kart hurts a lot more tho! I'll probably cap the lake pipes and see if I can fire it tonight
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Old 01-07-2013, 03:59 PM   #11
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Default Re: spark plug wire ohms

I have also used a spray bottle with water and sprayed the wires to test for spark leaks.
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Old 01-07-2013, 04:03 PM   #12
model A hooligan
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Default Re: spark plug wire ohms

Would this cause one cylinder to not fire at all? It ran fine last month, now it won't idle itself and at about 1500 rpm it's deffinatly not running on all 8. And I changed NOTHING
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Old 01-07-2013, 04:25 PM   #13
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Default Re: spark plug wire ohms

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Originally Posted by model A hooligan View Post
Haha I was messing with it the other day and got shocked.
if you got shocked while the wire was still on the plug, then it's a bad wire.
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Old 01-07-2013, 07:16 PM   #14
model A hooligan
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Default Re: spark plug wire ohms

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Originally Posted by hotroddon View Post
if you got shocked while the wire was still on the plug, then it's a bad wire.

Haha, good point
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Old 01-07-2013, 07:28 PM   #15
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Default Re: spark plug wire ohms

if the short is bad enough it can cause a cylinder to basically not fire at all. i would repl wires and go from there. how are your plugs? maybe getting fouled by the bad wires... just a thought
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Old 01-07-2013, 07:34 PM   #16
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Default Re: spark plug wire ohms

http://www.jalopyjournal.com/forum/s...d.php?t=734270


Just read this the other day...............
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Old 01-07-2013, 08:19 PM   #17
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Default Re: spark plug wire ohms

I have had wires that checked OK with the ohm meter,but would still miss under a load. sometimes just moving a carbon filled wire will make it separate internally.
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