Carbon Fiber plug wires

[irtrimble]

My engine was rebuilt here in Nova Scotia and came back with new plug wires. Are the new carbon fiber wires compatible with A4 ignition system?

[JOHN COOKSON]

Yes.
However:
Carbon core high voltage wires usually do not fare well in a marine environment.The insulation breaks down and the high voltage electricity gets outside the wire and shorts to ground (ie the head). Needless to say the spark plug does not fire.
When this is happening sometimes one can hear high a voltage snap. If you look at the wiring when it is dark sometimes you can see the arcing to ground. Misting the wiring will reveal the shorting more redly.

TRUE GRIT

[Dave Neptune]

Their probably actually "carbon core" not carbon fiber. Carbon wires are used mostly for radio noise suppression. And as Al pointed out they do break down.
Solid core wires were the norm and you have the replacements if you have radio noise.

Either wire type will easily handle the A-4 or a big block hot rod.

Dave Neptune

[capnward]

Solid core forever!

In the presence of gasoline, it seems wise to try to confine any sparks to the combustion chamber. I mystifies me why the insulation on carbon core wires would be less robust in a marine environment. Is the insulation degraded by moisture? Or by the carbon inside it? If it can't keep electricity inside the wire, it's not insulation. You would think the insurance companies and the USCG would frown upon the use of it.

[irtrimble]

From what I read, carbon plug wires are higher resistance, might decease voltage to plugs. Trying to figure out why engine is skipping and not idling well. rebuilding carb didn't help.

[Dave Neptune]

The higher resistance of the carbon core vs solid core is the same thing as a resistor/non-resistor plug. It is the resistance that increases the intensity of the spark by making a bit shorter in time and concentrated in energy IE the "whole spark" gets there and jumps over a shorter period of time or a bit more intense. I think one of the electronic guys could explain this much better.

The wires break down from heat and vibration. In the cored wires the carbon powder will begin to form gaps which add to the resistance however once the resistance is high enough the spark can find an easier path to ground than the plug itself. Solid wires will leak to but it is through cracks in the insulation. The newer silicone type wires are a worthwhile upgrade whenever replacing wires as the silicone just lasts longer and has far more heat resistance.

Dave Neptune

[JOHN COOKSON]

Trying to figure out why engine is skipping and not idling well. rebuilding carb didn't help.

Are the spark plug wires on the plugs in the correct firing order, 1-2-4-3?

TRUE GRIT

[irtrimble]

wire placement is correct. running a little rough as if not all cylinders are firing all the time

[Marian Claire]

Have you tried removing one wire at a time when the engine is skipping. You may find one that when removed does not make a change in how it runs.
Dan
S/V Marian Claire

[joe_db]

Look at your engine in the dark. I once saw blue sparks all over Time for new wires!