Using carbon HT leads with acorn caps...

[Bob Culver]

Cross firing from induction is more a problem with V8s where other cyls are within firing range of tdc. As I have recounted before in the 1960s I used to give a colleague a lift from our hometown on Sunady evenings. Although no definite pick up time he was always waiting outside the front door...saw me coming on the TV! Some claim the carbon in other later distributors was resistive giving some suppression. The pri side of unsuppressed ign on an oscilloscope is a bewidering mess. 
The manual advance cars are prone to leads coming loose at either end.