328 Electrical Issue - WTF?

Major bad connection. Replace the wire ASAP.

 

ignition wires carry around about 20,000 volts. When the insulation gets worn or cut or even when there is conductive contamination this is what happens, it's not uncommon.

 

As stated above...BUT, looking at the video it appears that the sparks are traveling from the nose of the coil to ground as opposed to from the wire to ground. The coil nose could have a crack or be carbon-tracked. Neither item can really be fixed if that is the case though I have heard of people temporarily "fixing" the problem with gobs of silicone slathered over the tracked/cracked area! It might work; it might not. New wires and/or plugs MAY also correct the problem by providing a less resistant path but they might not.

I think what I'd do first is check the coil for cracks/carbon tracks. I'd replace the coil if I found them but you might try the silicone approach. Regardless of how that check turns out, I'd then check the wires for resistance with a multimeter - Assuming they are resistance wires, as original-type wires would be, 7000 ohms per foot is a fairly common good number. Anything much higher would indicate excessive resistance. Then I'd take a look at the plugs. For that matter, if they haven't been replaced in some years, I'd just replace them anyway.

Again, if the resistance in the secondary wiring is high, new wires/plugs might stop the arcing by providing a path of less resistance but if the coil is cracked or carbon tracked, anytime it gets damp (washing the car, rain, fog, very high humidity) the arcing will probably occur again. The more it occurs the more the problem will increase until eventually, the path of the arcing will become the "preferred" path.

FWIW, in the old days (of which these cars are part of) a common "test" of the secondary was to have the car in the driveway after dark, open the hood, spray some water over the engine and start 'er up. It can be quite the light show and quickly identifies problem areas in the secondary!

 

Probably not, unless you're seeing heavy condensation on the interior of the bubble.

 

Just to start with the simple stuff, make sure that the primary wire is plugged in at both ends, coil and distributor. The swap that wire from front to rear bank and see if the problem stays .