In the past I have had some trouble with distributors on our 1937 Ruby, fitted with a two bearing engine, one shed the pin on the gear wheel and another threw off the automatic advance weights! I think that these problems were caused by too much end float on the dynamo shaft. I also found that the old distributors were inconsistent, sometimes the engine was too advanced and at other times retarded.
On hearing that a V/W distributor could be made to fit an Austin Seven I set about acquiring one and having it machined to fit. My thinking was that with a new Bosch item it should at least stay in one piece, and be consistent.
Having had a good look at what was needed, I decided to have some metal removed from the body of the distributor, this ensured that as much shaft as possible would be inside the gear to support it.
The accompanying drawing shows what needed to be machined off the body and the final assembly layout. The slide is needed to locate the body in the dynamo in the correct position using the setscrew.
NOTE: The points gap should be 17 thou not 12.
The new distributor was fitted and run in before the Pennine Run 2000. I set up the timing using a strobe light and the normal A7 specification, in all we covered 734 miles, and apart from boiling on a couple of hills and one oiled up plug the trip was trouble free. The extra mileage came from extending the Sunday run up to North Berwick for a family visit. The distributor was over advancing timing though. This resulted in a harsh sounding engine.
I then had a look at the innards of the new distributor and found that I was able to limit the advance very easily. The bob weight hits a stop to limit the travel, all I had to do was fit a pad to the stop and the job was done (see photo A). I also fitted a pad on the other side of the mechanism to preserve the static balance. A method for getting oil to the bearings needs to added. I did this by drilling through the case and fitting a tube and cup arrangement (see photo B). This needs only a few drops of oil to be added occasionally. To much oil will dilute the grease on the gears and contaminate the dynamo.