VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Spring loaded hold down bolt on '37 distributor

On my '37 there are two hold down bolts. The one toward the front of the car is tightened down firmly and the one to the rear has a spring under it and I am wondering what the function of this bolt is. Any ideas?

The front bolt retains the vacuum advance bracket to the block. The rear spring loaded bolt more or less holds the upper distributor clamp in place. The spring allows the advance to turn the distributor and still keep it stable and in place. A more simple single bolt system was used from 1939 and up. The original intention for 1937-37 was to make the distributor rotation smoother for the vac. advance.