Still working this idle misfire problem...

So I was measuring spark plug wire resistance the other day and this time I measured mine against my dad's wires on his Camaro. I'm running factory GM L98 Corvette wires and he's running GMPP wires.

His are measuring in the ~600 Ohm range. Mine are in the ~7000 ohm range. Wondering if somehow the factory wires aren't cutting it at idle speed. With a very similar cam and heads on a 350, his engine idles with a carburetor A LOT smoother than mine.

Maybe my wires are sufficient for a factory L98 TPI engine, but not a heavily modified one like mine? I know I have almost 20° more intake duration than a factory TPI cam; and I'm also running about 10.1:1 compression vs the Vette's 9.8:1. Could there be anything to this? I suppose one thing I could try is to run his wires on my car one day and see.


EDIT: BTW, just recently I burned out an MSD coil, so I'm wondering if the wire resistance is too great for my application.
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Pro-Touring 71

1996 LT4 Corvette Wheels are 17x8.5 front, 17x9.5 rear
Wheel adapters are 2.0" front, 2.5" rear
Baer Brakes four wheel discs
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Comp Camshaft, TH700R4 Transmission.
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[This message has been edited by ULTM8Z (edited October 10, 2005).]

[This message has been edited by ULTM8Z (edited October 10, 2005).]

you may be on to something. i cant remember what the specs were and cant check right now(at work) but when i bought a set of msd wires a bit back they had an ohms per foot spec. anything out of spec was too much for optimum performance.

I guess I'm not really after "optimum" performance so much at this point as I am adequate peformance such that this car idles smoothly. The big question is, is there a point where factory wires just plain won't work properly on a modified engine?

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Pro-Touring 71

1996 LT4 Corvette Wheels are 17x8.5 front, 17x9.5 rear
Wheel adapters are 2.0" front, 2.5" rear
Baer Brakes four wheel discs
Fuel Injected ZZ4, custom burned EPROM, AFR heads, TPIS Mini-Ram intake,
Comp Camshaft, TH700R4 Transmission.
God Bless the USA
Project Photos on ULTM8Z project photo album (http://photos.yahoo.com/ultm8z)
See me in Chevy High Performance (http://chevyhiperformance.com/featuredvehicles/86018/)
ULTM8Z Website (http://www.ultm8z.com)

[This message has been edited by ULTM8Z (edited October 10, 2005).]

Are you using spiral wound wires? MSD usually recommends (requires) that you use them, don't they?

7K ohms is pretty high, I would expect around 3K/foot from a stock wire
TPI engines are famously hard on plug wires, espically the boots. The angle of the spark plug in the head puts the boot really close to most manifolds/headers.
MSD offers a ultra hi-temp boot now, they are orange in color. Use those on your next set of wires

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1971 Camaro
383 stroker ~500HP
M21 4spd
12" brakes
16x10" Wheels
Autocross competitive
Engine Designer - The Speed Merchant, San Jose, CA
http://www.speedmerchant.com/

I would agree with Lowend- 3k ohms per foot is approaching the limit of what you can use- and any wire no matter what the length over 10k ohms is useless- this assumes a stock ignition system and one with a higher-output coil. I can't answer your MSD issue- but the fact you're running a modified TPI setup would tend to push me in the direction of a bad default A/F-timing map instead of blaming the wires if none are over 7K ohms.

Your wires are junk

<font face="Arial,Verdana" size="2">Originally posted by Rick WI:
Your wires are junk</font>

So waddya tryin' tah say? http://www.nastyz28.com/ubb/wink.gif


Man, I seem to be getting all sorts of different responses... posted in a few other forums as well. Some people say no problem, others say replace them for sure.

Hmmm, next time I get over to my parent's house I'll have to try my dad's wires and just find out. Anyway, just thought I'd get some opinions.


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Pro-Touring 71

1996 LT4 Corvette Wheels are 17x8.5 front, 17x9.5 rear
Wheel adapters are 2.0" front, 2.5" rear
Baer Brakes four wheel discs
Fuel Injected ZZ4, custom burned EPROM, AFR heads, TPIS Mini-Ram intake,
Comp Camshaft, TH700R4 Transmission.
God Bless the USA
Project Photos on ULTM8Z project photo album (http://photos.yahoo.com/ultm8z)
See me in Chevy High Performance (http://chevyhiperformance.com/featuredvehicles/86018/)
ULTM8Z Website (http://www.ultm8z.com)

I thought 2K per foot was about the top end of the acceptable range, but I never leave wires on long enough to have a problem like that. I usually burn them clean through on a hot header LONG before I have to worry about them wearing out!

Just be careful about what types of wires you use. Many of the low-resistance wires are not recommended for fuel injected engines. All the electronic stuff can be very sensitive to EM interference and such.

What I'm sayin is they are very high. New MSD or Taylor wires will be, at most, around 150-200 ohms. I have measured a lot of these with the ol Fluke 88.