I see the arcing. Usually that's a faulty plug cap or wire, or both. In the points/coil days, carbon tracing on the inside of a distributor cap could cause what you see. A cracked distributor cap was also prone to do that, as was water inside the cap, not uncommon after blasting through standing water.
You may not want to hear it, but I'd say new caps/wires/plugs are in order. Even if you replaced them a short time ago.
In horror movies, you've seen the static electricity generators like a Jacob's Ladder, where the horizontal spark jumps between two vertical conductors, and it moves upwards? Then the Van De Graff ball, which when you touch it, your hair poofs-out (assuming you have some) in a wild bigger-'n an Afro 'hair-do?' It appears that your components are allowing a significant leakage of your ignition energy to go to ground of the cylinder head. Hence you have those l-o-n-g sparks escaping from your components, and going to ground.
Just what you've done, seeing how the excess voltage pattern spreads from the ignition components to the grounding mass of the cylinder head is how we used to do it, searching for signs of failed ignition components, in 'the old days.' I grew up when you could go to KMart and buy a cardboard and bubble-wrap package, containing a new condenser, a pair of ignition points, a distributor cap and a rotor, for maybe five bucks. Then you would buy however-many spark plugs of the proper letter/number combo. Along with that, maybe 4 or 5 quarts of 30-WT and an oil filter, and you had a nice way to spend a day, or part of a day, if you're quick.
I think your components have failed, somewhere, somehow, Maybe not all of them, but certainly on the cylinders where you have the Frankenstein-effect.
You may not want to hear it, but I'd say new caps/wires/plugs are in order. Even if you replaced them a short time ago.
In horror movies, you've seen the static electricity generators like a Jacob's Ladder, where the horizontal spark jumps between two vertical conductors, and it moves upwards? Then the Van De Graff ball, which when you touch it, your hair poofs-out (assuming you have some) in a wild bigger-'n an Afro 'hair-do?' It appears that your components are allowing a significant leakage of your ignition energy to go to ground of the cylinder head. Hence you have those l-o-n-g sparks escaping from your components, and going to ground.
Just what you've done, seeing how the excess voltage pattern spreads from the ignition components to the grounding mass of the cylinder head is how we used to do it, searching for signs of failed ignition components, in 'the old days.' I grew up when you could go to KMart and buy a cardboard and bubble-wrap package, containing a new condenser, a pair of ignition points, a distributor cap and a rotor, for maybe five bucks. Then you would buy however-many spark plugs of the proper letter/number combo. Along with that, maybe 4 or 5 quarts of 30-WT and an oil filter, and you had a nice way to spend a day, or part of a day, if you're quick.
I think your components have failed, somewhere, somehow, Maybe not all of them, but certainly on the cylinders where you have the Frankenstein-effect.
