Does your rotor button look like this?  Is the contact held onto the plastic with a rivet?  If so, you may experience a misfire or ignition failure.  The original Lucas rotor contacts were recessed into the plastic and did not use a rivet.  On these rivet designs, the bottom of the rivet ends up being very close to the spring clip on the underside of the rotor, which means there is insufficient insulation between the contact and the distributor shaft.  Electricity follows the path of least resistance, which in this particular case means it grounds out through the rivet on to the spring clip and then to the distributor shaft, all of which means no spark to your plugs.  We replace these when we come across them to avoid ignition problems.  If you’re having ignition problems, this is a good item to put on the checklist.