Spark arching help - Team Camaro Tech
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post #1 of 13 (permalink) Old Oct 13th, 10, 02:14 PM Thread Starter
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Spark arching help

I have a 350 crate (300hp). I recently changed the distributor to HEI (modified point distributer), ran a new power lead-bypassing the old lead, changed out the plugs, new MSD wires--which I labeled and replaced in the right order, new coil, added electrical grease to all caps and I have a intermittent miss (you can hear/feel it and see it on a vaccum gauge) and a lot of arching around the boots, and at the looms. The plug gaps are .035.

Could this be a ground issue? Any suggestions of where to go next?

Thanks
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post #2 of 13 (permalink) Old Oct 13th, 10, 03:53 PM
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Re: Spark arching help

Think of the Ht as water in a hose...
The voltage is the pressure...If the leads, boots etc are not up to scratch, like a hose it will burst...A classic illustration of this is if you use orginal 4mm HT leads on a Std GM HEI you will blow ting pin holes in the side of the lead, just visible to the eye....I know this because I did it yrs ago (against advice) when went to the HEI

The other cause is a gap to wide...now the gap is not just the plug gap..it is the total gap between the rotor and dizzy cap pins PLUS the spark gap.
If too big it is like putting a nozzel on the end of the water hose, and blows holes or leacks thru joins

Another common cause is corrided contacts each end of the HT leads to the clips...
I have not purchased a ready made set for 30 or 40 yrs now, I buy a length and make up my own....when crimping the ends I use a small bit of copper or stainless wire, bent into a small U ends just under 1 cm long with one end pushed up into the HT lead, the other held in the crimp

Another common issue is some idiot pull the leads off a plug by the lead, and NOT by the boot...this damages the inside of the leads and is the most common issue for a dud lead, and often not picked up by the ohm meter.....and a common issue when boots are fitted

I NEVER use electrical grease to get boots etc onto HT leads....a very small squirt of silcone into the boot and light smear on the HT lead... work the lead thru the boot then put on the clips, wipe off clean then work the clip back into the boot.

A dud spark plug ... If you drop 1 or a box, just throw it away...1 reason why I have carpet in the workshop under my cars.

All of the above can also cause the effect mentioned above, of putting a nozel on the end of the hose and blowing a hole in the side of a lead

I also note here....I do not need to have boots on any of my spark plugs...good leads, good connections good plugs, rotor, cap pins....will not get a miss or a jump....I do run boots normally cause makes easier to pull leads off when things are hot.

I have used top gun ss spiral wound black 8 mm leads for near on 30 yrs, in near 200,000 miles Im on my 2nd set....I also use them on my old 6volt vintage cars, only swaping them for the 1920s sytle cloth HT leads for shows.

To check for leaks... open the hood on a dark night...you will get a little induced 'glow' thats ok....move the leads around and you will see hear the spark jump...and if brave with a good ticker (heart) run you hands down them with rubber soled shoes, and dont touch the car

If leaks then cant be found look at #5 and # 7 leads chevies where bad for crossfire (induced spark in the other lead) between these 2 if put too close together....the old pionts 6mm leads where far more suspectable to this than modern 8mm HEI systems.

My Spelling is not incorrect...it is creative

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post #3 of 13 (permalink) Old Oct 13th, 10, 04:49 PM
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Re: Spark arching help

Suggestions Steps gives are true. You need bigger plug wires and set your plug gap to min 0.045".

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post #4 of 13 (permalink) Old Oct 13th, 10, 05:50 PM Thread Starter
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Re: Spark arching help

Thanks for the ideas. The wires should be ok-- 8mm and brand new. What surprized me was the number of archs. If I had to guess it was the inner two 3,5 and 4, 6 that were more active. Also, I noticed the arching at the looms--metal four gaps. That seemed strange to me given that the wires were new--that is why I thought a ground issue.
The plugs are AC and have been on my shelf for awhile. I didn't want to push things so I gapped them at .035--shouldn't the smaller gap take some of the load off the system?
I'll see if I can isolate one or more of the plugs that are linked to the miss.

Thanks again, all good ideas.
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post #5 of 13 (permalink) Old Oct 13th, 10, 05:53 PM Thread Starter
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Re: Spark arching help

One quick follow up. Do any of you know the failure rate of new plugs? A guy I was talking with said that recently AC was having some quality control issues. I picked AC for no good reason other than thats what the engine came with. Are there better choices?
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post #6 of 13 (permalink) Old Oct 13th, 10, 06:35 PM
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Re: Spark arching help

View the wires at night. Ground strap from engine to firewall?
Autolite's. I'd remove the electrical grease - if you don't get the right kind, it is an insulator. Alcohol cleans very well, wood alcohol does a better job of cleaning, but you have to ask the pharmicist for it because it's posionous.

Maybe get plastic looms.

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post #7 of 13 (permalink) Old Oct 13th, 10, 10:20 PM
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Re: Spark arching help

I have used universal thinners on my leads etc for yrs...wipe on wipe off.

Plug failur rate.. I can only speak for NZ
back in the 70s ac where crap, a couple duds oin a champion box put me off and the jappa I had at the time had NGK, and these had just come on the market in NZ
Used NGKs ever since....I run LPG and that is VERY sensitive to spark..the slightest fault back fire on cold start up....no messing around new set of plugs.
NGKs when one drops out the others tend to follow very soon after,,,dont ask me why.

Quote:
The plugs are AC and have been on my shelf for awhile.
Thats scarry...I buy a box at a time and run 2 heats...I NEVER store pugs on a shelf, always in a draw and not loose....do not under estimate the fragility of leads or plugs

Basically everything that can go wrong is in my 1st post
Over the last 40yrs I have had to deal with damn near every one at some time sometimes several at once because 1 caused another.

My Spelling is not incorrect...it is creative

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post #8 of 13 (permalink) Old Oct 14th, 10, 08:59 AM
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Re: Spark arching help

I had a set of MSD wires that i put on last year that arched like I was in a thunder storm!
brand new too?


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post #9 of 13 (permalink) Old Oct 14th, 10, 03:35 PM
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Re: Spark arching help

I mentioned above that I buy my HT leads direct off the reel
When I do I donot buy of the last few meters or the 1st couple meters, and always dump the 1st couple coils.
This elimates some factory workere or guy in the shop jat grabbing the lead and yanking on it rather than rolling it off the reel.
got caught with that once...an old school auto sparky suggested that when I was scratiching my head.

My Spelling is not incorrect...it is creative

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post #10 of 13 (permalink) Old Oct 19th, 10, 09:46 AM Thread Starter
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Re: Spark arching help

Update: I replaced the distributer cap and this alone cut down the arching by over half.

So the notion that caps make a big difference is confirmed.
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post #11 of 13 (permalink) Old Nov 4th, 10, 08:43 AM
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Re: Spark arching help

Did you use dielectric grease? I use dielectric grease on the plug ends of the boots and have never had the issues you speak of. Just a tiny bit inside of each boot and spread it thin with a Q-tip. Also, if I bought a new set of wires and they were leaking that bad, I would be taking them back. From your description of the arc jumping all over the place, I think you might have used too much grease or the wrong type of grease.
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post #12 of 13 (permalink) Old Nov 9th, 10, 01:13 PM
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Re: Spark arching help

You'd be well served replacing the plug wires. As steps's analogy of HT electricity to water in a garden hose, the new hose shouldn't be leaking.
Add me to the list of guys here who've had bad wires. Mine were just last winter. Car barely ran. Vendor=nameless.
So,,,, any luck?

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post #13 of 13 (permalink) Old Nov 9th, 10, 10:34 PM
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Re: Spark arching help

I have gone thru 4 sets of HT leads in 30yrs daily driving
going from 6mm to 8mm pionts to HEI
A set of named yellow that sucked...To a then little know brand of Top Gun spiral wound black leads and couldnt get sets in a box...never liked black leads..
The next the same as the above...these leads have fallen onto the cast manifolds alsorts of horror...except NEVER been pulled on during making or maintaince.
LPG.... that stuff is real sensiive quality of spark....coil to elecrode.

Plugs I get 3 to 5 yrs out of NGKs
I get a slight miss fire, I buy a new set of plugs on the way home
IF I ran one of those MSD things (lol) maybe the plugs will not need replacing and make sure I get a fire...
But I would not know that I do still have a plug or lead going down.....

My Spelling is not incorrect...it is creative

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