While testing my plug wires in a semi dark garage I noticed the 7mm Packard 440 copper core ignition wires were leaking (spark mid cable to head.) There must be some cracks in the insulation of these older wires.
Was fiber covered plug wire (various colors) used on the early (1950’s) Jaguars? I have only seen 1 engine that had this type of spark plug wire.
'56 Mk 1