Hi I have a plus 4 but not used for some time ,however I had a very similar problem with my 1967 sunbeam alpine ,new coil several new rotor arms and several new condensers,I was then lent a swift tune condenser ,that sits out side the distributor ,easy to wire up,and cured the problem.Its about £30 odd but having spent more than that on rubbish new condensers ,it was worth it