25-09-2021, 08:24 PM (This post was last modified: 25-09-2021, 08:31 PM by Bob Culver.)
The tail is to accomodate the centrifugal auto advance range. Cras with little or no auto advance require no long tail. More insulator materiel assists balance.
(For decades I have run a 1964 Minx. For most of that time the car was not easy to start idled poorly and did not slow run smoothly. It rapidly eroded the cap studs. eventually the rotaor sprked through. It transpired the spark was firong beyond the end of the brass. Everything was stock although the conatcts had been repeatedly restored by stoning so these and the rubbing block were much reduced. Remedied by attention to the vac advance adj and all much improved)
With most ignition systems spark duration is several degrees of revolution so some wdith/length is desirable. (I presume this explains why cars with failing igniton run with reduced power but not actually missing. The effective firing occurs late)