I've never been much for "...oh, I think that's OK..." when it comes to rebuilding distributors. The engines that get my rebuilt distributors don't think much of guesswork, either. This picture shows a special tool that I built, a MightyVac and the data sheet that records exactly what was done to a typical distributor and the results of the rebuild work.
I plot out the curves--shown on the data sheet--for mechanical advance [top] and vacuum advance [bottom]. The mechanical advance curve is checked on the SUN distributor machine. I correct that curve by taking the distributor apart and changing advance springs. Testing it again on the SUN machine tells me if I managed to get the correct springs or not. This can go on....and on....I call it the perverse nature of inanimate objects....
This is the tool I built to test the advance curve of any Bosch vacuum advance unit [the silver "pot" mounted on the tool at the bottom of the photo]. I attach a MightyVac to the vacuum advance unit and start applying vacuum to the advance unit. I read the vacuum applied [on the MightyVac dial] for each degree of advance [shown on the scale at the end of the red tool. I record that on the graph on the data sheet.
Another view of the tool. The scale at the end is calibrated in degrees, taken off a precision protractor. It's a lot of screwing around to make an old, nasty, dirty, tired, worn-out distributor like new again! But the engines my distributors go into think my time was well worth it. A guy told me once he thought I operated in a vacuum. I told him I probably did but it was a precision one.
City Car Design
6 years ago