Commonly referred to as the Top Hat Piece. Royal PITA to replace.No, not the insulator. The shaft that the rotor rides on is not insulated in any way from the shaft that goes all the way down, but this little plastic thingy is supposed to keep the rotor shaft from sliding up far enough to disengage the mechanical advance.
I started looking at the distributor replacements - DUI is $600 and lead time is three months. Ordered myself a stock replacement, so I have one around for three Classics.
Speaking of spark coming out of the coil but not out of distributor... It can easily be distributor timing way off.