Well I finally found a downside to the use of a Pertronix electronic ignition conversion.

I fitted one to my 1200 years ago & have NEVER looked back. I have never looked at the inside of the distributor again either & that was the problem.

During routine maintainance with points one is supposed to lift the rotor button & place a drop of light oil in the hole underneath the rotor. This lubricates the distributor cam & the distributor shaft so that the mechanical advance can work properly.

Well of course without points, or the need to lift the cap & rotor, the shaft never got oiled & it eventually stuck in just one position which means that the mechanical advance function ceased to, ..... well, ..... function.

I found this when troubleshooting another problem, so I gave it a drop of oil & freed up the stuck parts. All is well again & I will perform this service task at each oil change in the future.