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Plug wires arcing to the header through wire sleeve
So I have a swapped car with some tight clearance around the spark plug wires and headers. it misfire a little bit but it is getting worse and I can see the wires arcing on the headers bolts on at least two wires.
I had to use the shorty accell plugs and make my own wires.
Actually I modified some multi angle MSD wires. I replaced the long straight boots with some short 45deg boots. On cylinder #7 the wire would touch the header, and one some others it will be very close to touch.
Now I'm trying to figure out what I could do to avoid the arcing...and maybe what I did wrong.
I used some PL100 lube to slide the plug wires boots on the wires. Could that cause the voltage to short on the boot?
I used some Taylor spark plug wires heat sleeve. Supposely these can touch the header and deal with it fine... but I could see the arc going THROUGH the sleeve to the header bolt... are these boots conductive???? If I could see the arc, it mean that this was on the wires that the sleeve DO NOT touch the header or the block... actually the sleeve with the best clearance...
Also I tried the accel ceramic one with the 135deg boot, but it wont fit on at least 2 cylinder (including 7 which has the worst clearance).
The plug wire sleeves are worthless. I kept melting wires with the sleeves on so I took them off and it stopped melting wires. I think the sleeves hold the heat in making it worse.
Re-ground the engine, and around the coils. Give the coils a very low resistance pathway to the plug, and engine block. Make sure there is a nice fat cable going from engine -> chassis and then chassis -> battery in multiple locations.
Spark avoids the plug when it finds a better pathway. So make the pathway away from the plug more resistive (adding insulation does this). If you added insulation and the pathway is STILL looking better than the engine block/ground, then you are obviously missing a serious ground or overlooking something in the construction of the wire pathway.
Thanks for the tips, I'll add some additionnal ground from the battery to the chassis and from the chassis to the battery when I get back home to see if it helps. For now I have a 1/0 wire from the negative to a roll cage bolt and the engine ground is a gauge 1 wire from the passenger head to a bolt that attach the remote oil filter mount to the passenger frame rail (bolt is threaded directly into the frame rail). I thought that would be good enough but adding more grounds for testing is easy and inexpensive.
I don't think I've melt any wire yet, I've only done some mild street driving, I haven't push the car much yet. For now I think I'll keep the thermal sleeves unless I melt a wire with them.
I'm probably going to get some new spark plug wires too since these have arced. From what I've read this has created an inductive path for the voltage to escape on the wires... this suck.
Hopefully this will be enough to cure my misfiring/arcing problem.
Grounding is not your problem, obviously you have a crack in the insulation of the wire, you plug sparks from the inside which is ceramic insulated to the outside of the plug which is grounded via being screwed into your block. So, either you have a cracked plug or your wire is cracked and letting voltage leak through. My 2 cents. Peace...
Running grounds thru the frame IS NOT a good practice.
This topic is constantly being cussed, discussed, and debated.
Try a search, and learn from that.
So two wires burned through the sleeve. I bought some Taylor wires and decided to try making some bracket that bolt to the head to keep the wire away from the headers... I can't use the sleeves with the brackets so I'm hoping the wires will hold up with a bit more than 1/4" of clearance. The brackets are some steel flat I shaped...i hope they won't heat up to the point of melting the wires.
maybe try some of the sleeve that actually goes over the wire itself. like the accel pro sleeve type product. i use nascar take off wires that have a similar product made by champion on my turbo truck.
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Plug wires arcing to the header through wire sleeve 
