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Cylinder #5 will not stop arcing off header!

Y

Yo

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I'm at my wit's end with this problem.

My truck is a 1991 K5 with a carbed ZZ4 350 swap.
It uses an MSD6A ignition and a super billet distributor without vacuum advance. MSD 8.5 wires, and the Champion plugs specified for the ZZ4 (can't remember the part# off the top of my head...).

Motor generally runs amazingly, except for one issue; no matter what I do, my #5 cylinder wire will eventually start arcing out on the header. Here's what I've done thus far:

-Moved battery ground off point on AC accessory bracket to frame (PO rigged this setup :doah:)
-Added a zero gauge ground wire from the fuel pump block off plate to the frame (truck has electric pumps, this was the most available/easy spot for grounding)
-Tried both 90* and multi-directional plug boots
-Tried using high temp boot sleeve (arcs through the sleeve!)
-Added zero gauge ground wire off passenger cylinder head to frame
-Swapped 8.5 to 8 mm plug wire
-Swapped plugs

This is most problematic upon acceleration and during idle; wire will arc and make a very distinctive "pop", engine sounds like it chokes out, then comes back, which clearly must be hard on the motor. It happens more frequently when the motor is hot, which makes sense. Could this also be a something triggered by the lack of a vacuum advance, since it seems to be most prevalent when accelerating/idling?

I called MSD and Summit's tech lines, and both agreed the issue was ground related; MSD sent me a new plug wire with a high temp boot that was promptly destroyed after 3 miles driving. Even after having added two separate ground wires off both cast iron and the offending aluminum cylinder head (I know aluminum is a weak conductor, but it was a last ditch attempt at grounding the head directly), the problem persists.

Any suggestions?:confused:
 
How much clearance is there between the wire and the header? How does the coil ground? Sure it could be the grounding, but what makes #5 special?
 
I would say change the plug, boot and wire, but I see you've already done that.
How close to the header tube is the wire?
Can you hang the wire so that you increase the distance?

Btw aluminum is a much better electrical conductor than iron.

And I would advice you to get a distributor with vacuum advance, unless it's a pure race-engine.
 
is it too hot and close to the header?that would melt the boot and cause the wire to ark.also too hot of a spark plug could heat up and melt the boot.but it is highly unlikely since they are quality high heat wires.champion plugs are not very good anymore and ive had nothing but problems with them in the last few years.i have been using autolite plugs and gap to .038 seems to work best.i have msd 6a also with high power accel super coil and pickup rotor and cap.and use the standard autolite plugs for smallblock 350.try changing plugs and see what happens.definitely sounds like the header is too close to the plug.you may need to finess the header away from the plug with a hammer.heat up the engine real well and tap the header by that plug with a hammer and it will move maybe far enough away to keep the heat off the boot and wire.
 
The quick answer is, there is too much resistance somewhere along the #5 cylinder as electricity follows the least path of resistance. Since you've already replaced the plug wire my guess is either a bad spark plug or too much fuel getting to that cylinder causing enough resistance that the spark goes through the plug wire or boot to ground rather than through the spark plug to the electrode. It would be more common for it to be a spark plug issue than anything else, and with that being said I started running the NGK V-power plugs some 20 years ago and have never looked back as i've NEVER had an issue with those plugs.
 
4X4HIGH said:
The quick answer is, there is too much resistance somewhere along the #5 cylinder as electricity follows the least path of resistance. you've already replaced the plug wire my guess is either a bad spark plug or too much fuel getting to that cylinder causing enough resistance that the spark goes through the plug wire or boot to ground rather than through the spark plug to the electrode. It would be more common for it to be a spark plug issue than anything else, and with that being said I started running the NGK V-power plugs some 20 years ago and have never looked back as i've NEVER had an issue with those plugs.
Click to expand...

The resistance issue is what puzzles me. I hadn't thought about a rich condition over-saturating that cylinder, but the spark plug does not appear to reveal a rich condition. I snapped a few pics; the plug has probably 1/8-1/4" from the header.

BTW, plugs are Delco MR43LTS gapped at .040 as instructed by GMPP.

4895611806_04d44e204c.jpg

4895610934_b1903886a5.jpg

4895610034_d80ebf521f.jpg

4895013887_e696a41040.jpg
 
That header design is just stupid.You have two pipes heating the helll out of that boot.Lookes like an oven.:eek1:
 
Yo said:
-Tried using high temp boot sleeve (arcs through the sleeve!)
Click to expand...
This is probably obvious, but you used the sleeve with a new wire, right? The sleeve is only resistant to heat, not high voltage. That header design is challenging. I think you'll need extra protection. You know how a lot of newer cars have an aluminum heat/RF shield around the boot? Why not try something like that? Those MSD wires might leave enough room for the metal shield + the high temp sleeve.

Are you 100% sure that this wire is snapping onto the plug correctly?
 
From the looks of that header tube I would be using one of the 90* boots that is rated for 1200* and come straight up from that plug and not between those two tubes.

Also, are you using the die-electric grease in the boots? If not you should as it helps with installing the plug wires, it eases removal of them AND it acts as a water barrier to keep water out of the boot.
 
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Aluminum is not a week conductor, it conducts better than iron.

Also I don't necessarily think this is your problem, but the main battery ground cable should go straight to the front of the block, not to the frame, and then to the block and too the head. But as many grounds as you have it probably doesn't matter, as long as all of the connections are clean before you attach them (meaning stainless wire brushed bare metal clean).

I was going to tell you to use higher quality parts, but MSD wires are quality parts. I think you obviously need to route the wire away from the header as much as possible (if you can't get it out of the away enough below then try what 4x4High said), while adding a protective sleeve ON a new boot. And also you might need to try what hombre said and dent the header there a little so you have a little more room.
 
Get a new wire, switch the #5 plug with another cylinder and see if your burn moves. If I was you I would get some heat wrap and wrap those two primary tubes. Thats a serious oven and a very poor header design.

Is there a point to it btw?

O and :chainsaw: just cause I just saw this smiley.
 
I think a 90* boot is the way to go...



Ive used these sleeves. If they are touching the header at all it will turn white after awhile, and will no longer work. Plus they are expensive. I think with header tape, they might work a little better.

plug%20wire%20boots%2000.jpg
 
The 90* boot was my first fix, and of course, it didn't hold. The plug was the custom cut set with multi-directional boots, but MSD includes a few 90*. I gave that a shot and the wire blew just like the others; in fact, with this setup it would arc a little above the boot straight out the wire.

Heat is most definitely an accelerator in this whole dilemma, as the truck won't do this when cold, even if the wire has already started arcing. It
ll pick up when the truck reaches OT though.

I used a brand new wire w a brand new heat resistant boot and thermal boot, still no luck. Again, making new 8.5's, the wire will disintegrate sooner than with an 8mm, probably because of the greater clearance I get with the 8mm boot. The 8 will eventually arc though.

I guess my next move would be some new headers. Bummer. That's pricey, especially since my AC just took a crap YESTERDAY. Can't believe it, was working fine, then all of a sudden, I accelerated, and it blows humid and sounds like someone shaking a cookie sheet under the driver's side front. WEIRD. I can't even think ab this right now it makes me so bummed. It's over a 100* in TX right now....
 
Do yourself a favor, since you said these are the wirews that you have to "make" yourself it could be that you aren't getting a vewry good crimp on the conductor itself. Go to MSD's website and see what they want for resistance across the length of wire and check it to make sure it doesn't fall outside of the spec. This could very easily be the whole problem.
 
Could you have a vac leak at #5 that will make #5 run hotter. that plug wire isnt really that close from what I could see. Other than that get rid of those crap headers and get some dougs headers (not doug thorley) DOUGS or lemons, Hooker and hedman are S@#t H Food for thought
 
Here we go... Super conductor wires should read between 40 and 50 ohms of resistance per foot of wire. ie. if you have a two foot wire max resistance should read 100 ohms and so on.

Check the reistance when the wire is hot as well to see if the wire breaks down after the motor builds heat. If the wire is ok cold and has excessive resistance hot this may be your only issue.

On another note... since this is a custom wire set that you crimp yourself the distributor terminal is the end insatlled by the customer so if it were a bad crimp we'd have an issue at the distributor cap not the head.

What spark plug gap are you running? Let's see if we can get this solved.

-Phil
 
Pretty sure its heat. I would swap or replace the plug just to be sure, but a good set of wires should not arc through even if they are touching a ground.
If its cold.
So, if its heat, there are ways of handling heat.
If this was several years ago, it would be simple.
Asbestos paste.
Great stuff, great heat blocker.
Kinda hard to find now though.

But there are replacements. Unfortunately, I am away from my office, and do not have access to any of my reference manuals.

I would try a two pronged attack.
Put any kind of insulating coating you can find on the headers around the plug wire to try to keep the heat in, then some kind of reflective insulation on the wire to keep the heat from doing the damage.

What would really help, would be a ceramic tube around the plug boot, wedged or glued in the header not touching the boot.

I will look around to see what I can find.
 
Philly87 said:
Here we go... Super conductor wires should read between 40 and 50 ohms of resistance per foot of wire. ie. if you have a two foot wire max resistance should read 100 ohms and so on.

Check the reistance when the wire is hot as well to see if the wire breaks down after the motor builds heat. If the wire is ok cold and has excessive resistance hot this may be your only issue.

On another note... since this is a custom wire set that you crimp yourself the distributor terminal is the end insatlled by the customer so if it were a bad crimp we'd have an issue at the distributor cap not the head.

What spark plug gap are you running? Let's see if we can get this solved.

-Phil
Click to expand...

Idk if Phil works or is a rep for MSD but you cant beat that **** right there. Good company all the way around in my book :waytogo:

That being said I have 8.5 cut to fit super conductors on my truck and didnt exactly cut them to fit so theyre sorta wire tied all over the place. Point being that a few times I've popped the hood and gone "**** how long has that wire been layin on the header...." never had a burn issue...
 
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