cylinder #1 is the only one that isn't shrouded to the plug.. Cylinders 5 and 7 NEED it due to proximity to the header tubes..

Though I was at one point a hair from pulling the plug jackets out of the heads, I decided against it.. I'm glad I didn't.. They help keep this rig of mine off the pipes some.. I didn't realize I haven't zip-tied the tubes closed down around the plug wire until you asked me to take these pics.. on the passenger side, where there is more room- I pushed the heater core hose down into the plug sleeves (over the top of the gray plug boots) and zip tied them just behind where they bottom out..

It looks dang goofy-but it works.. And, like I said- that baby AIN'T going to cross-fire.. ever... Rubber over thread is a VERY suitable insulation for those wires.. Following basic electricity theory- it's going to follow the path of least resistance, and so long as they are well insulated, that means the spark travels down the filament from the cap to the plug- and nothing in between.. If they are well insulated, there should be very little static field around them.

 

The rubber insulation will have no effect on the magnetic field...

It will prevent the electrons from jumping to another wire, though air actually has a higher resistivity than rubber, so the only advantage to the rubber is for temperature insulation.

 

I don't wanna jack the thread. but I'd like to learn about what you're saying Grox.

for wires running in parallel, there is opportunity for inductance from one wire to the adjacent wire- but that inductance isn't going to be strong enough to push across the gap on a plug.. so dangers from misfiring from that are minimal, no? If this wasn't the case, would there not be terrible inductance taking place atop the distributor below the cap when the rotor spins its spark basically unshielded?

it has always been my understanding that aging (cracked) or overheated wires, or wires that were too poorly shielded for the current shooting through them would cause crossfires, and that was the issue for running parallel- that you just upped the opportunity for that to happen dramatically.. the inductance thing is an inherit issue, but again- it won't produce enough energy to jump the gap on the plugs themselves..

How screwed up am I? I'm not being smartarse, I'm seriously asking because I'm learning that I don't know near as much as I think I do! :-)

 

I know that a crack in a wire will allow the spark to exit at the crack and get through into another wire. I know because I melted the wire on cylinder #6 and it was jumping into #8. I had the 200-300 rpm surge at highway speeds and replacing that cracked wire stopped it cold.

I also know about the insufficient insulation deal because a grille starter that I was rigging for a tater gun a few years ago. I wrapped it up in electric tape (lots of it) and when I hit the button I saw the spark jump from the tip to the side terminal, through the electric tape. If you're going to play with a grille starter then don't hold it in your hand when you hit the button, it isn't a pleasant surprise.

I was thinking about getting those asbestos wire loom deals to put around my wire boots. I have mine clipped in the valve cover guides and ran in such a way that they're pulled toward the valve cover and not leaning out toward the headers any more. I also ditched the heat shields a few months ago.
I'm not worried about my wires with the absence of heat shields because they have a lifetime warranty on them so If I melt the boots then I'll put the heat shields back on and swap out the wires again.

 

The issue of a spark jumping from one wire to another is only one problem. This is caused by insufficient resistance between an area of high potential (voltage) and an area of low potential. Think of this like water behind a dam. The water (electrons) wants to flow downhill, so you build a dam (insulation) to stop the water.

The issue of inductance between wires is another issue. Moving charges create a magnetic field. So every time a spark plug fires, there are moving charges, so a magnetic field is created, then when the rotor turns and the connection is broken, the magnetic field goes away. This creates a changing magnetic flux (i.e. the magnetic field is not constant). According to Faraday's Law, voltage is created proportionally to the rate of change of the magnetic flux. So each time the magnetic field changes (when the rotor turns) a proportional voltage is created in the other wires. If this voltage is enough to overcome the resistance of the spark plug gap, the plug will fire.

 

Sure it will.

The resistance of air is more or less 2E16 ohms/meter, so that .001 meter spark plug gap presents an impedance of about 20E12 ohms. That's huge. Induce just one nanoamp into that circuit and you'll develop 20kV which is enough to get you to breakdown of that dielectric and a fired spark plug.

It's an easy experiment to set up. Just take an old but still good spark plug and wire, and loosely tie-wrap that setup to a good long plug wire on your engine like the #2. Clip a jumper from the ground electrode of the plug to a good ground, and make sure that the open (coil) end of your wire isn't near any ground. When it's good and dark and your eyes have adjusted, start the engine and take a peek.

 

damn it gents...

alrighty.. I'm heading back out with the TSB routing in hand..

and here I thought I was slick..

:-)

 

Build a faraday cage around your individual plug wires.

 

No they need to start building those in the cabin of every vehicle a woman purchases, cut down on the cell phone use.

 

Make it close enough to the body and maybe it'll cut down on makeup application and book reading at the same time.
That book thing isn't coming out of nowhere, I actually saw a woman cruising down the road one time reading a book.