Shielded wires not necessary...you sure?

[UTKarmann_Ghia]

I've read on this board and talked with my local wrench about replacing my plug wires. There were 2 of em which registered an open and all of the seals were toast. So, with the recommendation of my local wrench, I replaced them with German made ones (started with a 'B", cant remember the name). Everything I had read and heard said that the grounded ones were not necessary on my car. And the new ones seem to work just fine...But... I have a neighbor who's been working on air-cooler engines for over 20 years (Porsche and VW certified mechanic) and he was checking something on my engine while it was running. He was reaching down to remove my vacuum advance tube and "snap" he got shocked by my wires. He was surprised that I was not using the shielded wires. Did I just spend $100 on wires which needed to be shielded?

[island911]

The shielded do provide an extra layer of safety. Wires (obviously) don't need to be shielded for the engine to run. (and thats good enough for a whole lot of folks)

I suppose it all really depends on whether you want your (Porsche and VW certified mechanic) neighbor to occasionally drop by to help.

Strange though; I would expect the insulation (on the non-shielded wires) to prevent anyone from getting shocked by the wires. (?)

.. oh, and the shielded help cut down RF noise too.

[Jim Sims]

Shielded wires will not prevent one from getting a shock; in fact if the wire insulation is bad having shielding can promote shocks (along with engine missing). The shielding was added to reduce "cross-talk" between wires in hopes of alleviating the "blown airbox problem". It also, as already mentioned, helps reduce RF noise. The shock probably came from bad insulation, or an improperly seated boot or from something conductive (dried sweat will do) from the inside of the boot to the outside insualtion. I discarded the sheathed wires on my '76 two years ago and haven't had a problem with performance, RF noise or getting shocked.

[jmohn]

If he got a shock, that wire (shielded or not) is compromised in some way. The shielding really is not necessary.

Jerry M
'78 SC

[Superman]

Healthy wires do not shock people, though many ignition wires are not healthy, and grabbing them is always risky. When you grab the top of a distributor with the engine running, like when you're adjusting timing, just be prepared for some excitement. Again, good, fresh, healthy wires generally won't do that.

If a wire is inclined to do that, and if it is not coming near any metal parts, then that cylinder will probably fire just fine. No ignition "miss" unless you grab it or let it near another ground. But if a bad wire is leaning against an engine part, or if it is wrapped in steel which is grounded against the engine, then that electrical pulse will go to ground instead of to the spark plug, and your engine will have a "miss."

Matt, for these reasons and the reasons above, we still take the position that the stainless steel socks around your ignition wires is unnecessary at best.

As a side note, in the olden days when ignition systems generated 15kv or less, getting zapped was inconvenient and exciting but tolerable. Today's ignition systems generate ridiculous voltage levels. 30,000 volts is a weak system by modern standards. So, grabbing ignition wires while the engine is running is a much more, ummm, serious decision.

[stlrj]

You probably replaced your cables with stock non-shielded Beru wires. Unfortunately, Beru cables, even when new, tend to short out where the wires screw into the the plug or distributor connectors. For that very reason, I would stay away from the expensive/inferior Beru in favor of more conventional silicon cables that run directly from the distibutor to the plugs without a joint in between.

Cheers,

Joe

[island911]

Originally posted by Jim Sims
Shielded wires will not prevent one from getting a shock; in fact if the wire insulation is bad having shielding can promote shocks (along with engine missing). . .. .

Care to explain that? . . ..I'm not following.

I suppose that if the shieling isn't properly grounded, you would have a worse situation (w/leaky wires under braid) . . being that you nolonger need to grap in the vicinity of the leak, to get zapped.

Other than that, how can having shielding can promote shocks? What am I missing, Jim?

[Jim Sims]

Depends which path has the lesser impedance - through you or through the shielding braid and engine grounds (unmaintained 30 year old engine grounds can be rather poor). And yes, I've seen cars where the plug wire shielding braid ground connection was "flapping in the breeze". Cheers, Jim