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 Post subject: Plug Wires?
 Post Posted: Sun Oct 07, 2012 1:17 pm 
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I'm chasing a miss in my engine and was going to ohm the plug wires but I'm getting mixed info on what I should see on the meter?

Anyone have accurate info on what readings I should be getting on these wires on the 20K ohm scale? :-k They are 8mm and have the small wire wrapped around the core.


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 Post subject: Re: Plug Wires?
 Post Posted: Sun Oct 07, 2012 3:15 pm 
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webermaniac wrote:
Usually ~ 1 to ~ 8 kOhms for "general purpose" helically wound nichrome core wires; MSD wires are less, from maybe 0.2 kOhms to less than 1 depending on the length.


These are spiral wound core and I'm getting .1/.2 ohms on the 20K scale on all of them except the coil wire which is .08 but it only 14" long. Checked one on the 200 ohm scale and it was 148 ohms.

I suspect this more of a concern on graphite core wires like on a "stocker" as I know those usually read way higher than the spiral wound wires do.

It's basically only one cylinder so I'm going to "assume" that it's a plug that has failed early in life and put in a new set for Wednesday night at Roxboro.


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 Post subject: Re: Plug Wires?
 Post Posted: Mon Oct 08, 2012 6:06 pm 
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Ken,

Try a contact paste on the threads of your spark plugs. I have had good luck with this. Might not be a miss issue but you may be surprised at the results.

What kind of numbers are you seeing with the ohm meter. I'd look at the different wires to be about the same. should be an ohms per foot rating for the wire from the manufacturer.

Don

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 Post subject: Re: Plug Wires?
 Post Posted: Mon Oct 08, 2012 6:19 pm 
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want-a-be wrote:
Ken,

Try a contact paste on the threads of your spark plugs. I have had good luck with this. Might not be a miss issue but you may be surprised at the results.

What kind of numbers are you seeing with the ohm meter. I'd look at the different wires to be about the same. should be an ohms per foot rating for the wire from the manufacturer.

Don



Don, You want to explain that "contact paste" a little better???

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 Post subject: Re: Plug Wires?
 Post Posted: Mon Oct 08, 2012 6:46 pm 
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Check each sparkplug for continuity. Plugs have 2 joints inside the porcelain. The joints are done in a lousy sort of spot weld way. They look like the 2 ends of the metal have been forced together and heated. Anyway sometimes its not done that well and the joint either has high resistance or is open circuit. What happens is it heats up dramatically at the bad joints because its all encased in porcelain and the extra resistance of the heat stuffs the arc. A good jointed plug has a resistance to a multimeter of 0.5 ohm. If its more than 0.8 ohm the plug will fail. Vibration sometimes breaks the poorly done weld and the plug fails after a time period.


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 Post subject: Re: Plug Wires?
 Post Posted: Mon Oct 08, 2012 6:50 pm 
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What plugs you running Ken??

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 Post subject: Re: Plug Wires?
 Post Posted: Mon Oct 08, 2012 7:30 pm 
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Fix all of it.

http://www.firecore50.com/

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 Post subject: Re: Plug Wires?
 Post Posted: Mon Oct 08, 2012 8:46 pm 
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Beretta wrote:
What plugs you running Ken??


It had AR 3932s in it up until yesterday.

I had a fresh set of 5671A -10s here in the shop so they are in it now.

I had a second set of wires here from when I was chasing some MSD problems years ago and changed them out only to find that wasn't the problem. We'll take those with us Wednesday night to try in case the plugs don't fix it.

want-a-be wrote:
Try a contact paste on the threads of your spark plugs.


Never heard of this stuff but I do run never seize on the plug threads to keep them from horking up the threads in the head. Plug wires had readings around 150 ohms.

Shrinker, # 1 cyl was the one that was showing it was missing but I did find that on #6 the center electrode was BACK down in the porcelain about .050 further than the rest of them to where it was about flush with the end of the threaded housing. That one probably suffered the failure you mentioned.

Judging from what I've seen I'm guessing I got a set of either Friday afternoon or Monday morning plugs! [-(

Funny part of all this is that this stuff just started happening all at once. Time before last at Waynesboro we were 140+ off the trailer. Second pass it slowed a little but not more than one "might" expect from DA changes. Then I did a jet change and the result of that was that a float stuck open in the rear and THAT was the reason it fell off to 134 on that 3rd pass.

Fixed all that stuff then last Friday night off the trailer it only ran 130MPH??? Pit Bitch said it kinda sounded like it was missing down track but checking exhaust pipe heat in the pits didn't show me a dead cylinder as all eight would blister you if you left your finger on it for anything more than a split second. EGT on #1 showed it got cooler down track and when I looked at AFRs on that one showing above stoich that was what told me it was only missing under load down track and not at part throttle on the return road.

Ennywho, we're all set to go to Roxboro Wednesday night so hopefully these problems will be fixed and I can get a pass or two on that "B" Dominator that I've made some more changes to this past week.

Thanks guys!! ;-)


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 Post subject: Re: Plug Wires?
 Post Posted: Thu Oct 11, 2012 8:37 am 
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BAD NEWS!

It wasn't the plugs nor is it plug wires. Funny thing is it's slow as crap but it's also xerox copying time slips!! [-(

Beginning to think it may be the coil or the MSD box. And here I am with the best weather if the entire year and I got a horked up car!!

DAYUMNIT!


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 Post subject: Re: Plug Wires?
 Post Posted: Fri Oct 12, 2012 10:03 am 
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Talked to Kowalsky yesterday and he's got an extra coil for an MSD 7 series box that he will loan me to see if that is it. He also told me that he had a similar problem with his car last year that turned out to be the crank trigger pickup and on his car it happened just like it did on mine, ie, just all of a sudden started missing up top.

I've also got an extra crank trigger pickup so I'm going to swap that out first.

Also have an extra distributor that is the small cap Mallory I run with the tunnel ram that I'll take with me too.

Just a shame that I have to go to the track to test any of this stuff as it's not doing anything funky at part throttle or up to the two step on the trans brake @ 5K RPM. [-(

Seems like I have one of these episodes every few years or so. Hopefully I'll get this sorted out soon as there's only a few opportunities left before the season ends here. The way it is now I'm going to have to tow to Roxboro (190 miles round trip) or Piedmont (270 miles round trip) to test anything, which is really expensive with diesel at $4 a gallon now.


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 Post subject: Re: Plug Wires?
 Post Posted: Fri Oct 12, 2012 11:12 am 
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Yep happened to me also with the crank pickup!!!!! Ask Tony as he was at the track with me...I can give you some help there grab the wires where it goes into the trigger and wiggle them when it's running or tap it with a small hammer..Doing that made mine miss then shut off O:) ..

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 Post subject: Re: Plug Wires?
 Post Posted: Wed Oct 17, 2012 10:21 pm 
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It's the distributor!!

When the bolt came out of that rotor button it got caught up between the pickup coil and the wheel and it must have bent the shaft as today I checked the ignition timing again and it was only 18* where I normally run 30* on methanol?? O:) Checked the phase on the distributor and sure enough, it was off a fair amount so I moved that back to where it needed to be and went to the track tonight.

On the first pass it ran 5.08 @ 136 and was spinning the tires so hard down track that Pit Bitch said he could hear the tires crying all the way out the back door.

And then on the second pass it fell off in high gear again out past the 330 timers after it did the BEST 60 FT TIME EVER @ 1.119?? O:) Checked and the distributor had moved again??? So I re-phased the distributor.....again and went back out and proceeded to run another 5.08 @ 136.

So now I know what's wrong so I'll be looking for an old stock GM points type distributor to replace this bent shaft MSD one! Anyone have one laying around for cheap?? ;-)

And I was REAL happy to finally figure out just WTF was wrong! \:D/

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 Post subject: Re: Plug Wires?
 Post Posted: Thu Oct 18, 2012 6:28 am 
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Ken my neighbor has a Mallory unilight (sp) that he got at a swap meet that he my part with???
Will that work for you =;

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 Post subject: Re: Plug Wires?
 Post Posted: Thu Oct 18, 2012 6:59 am 
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Beretta wrote:
Ken my neighbor has a Mallory unilight (sp) that he got at a swap meet that he my part with???
Will that work for you =;


Already have one of those that you gave me a couple of years ago to run with that tunnel ram. Remember? Like the larger cap though so that's why I run the MSD with the LT1 style cap. The larger caps do have "somewhat" of an advantage as it's harder for them to cross fire.

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 Post subject: Re: Plug Wires?
 Post Posted: Thu Oct 18, 2012 7:22 am 
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OK how about a HEI dist that has locked advance from a late model GM??? No vacuum advance or mechanical adv..

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