25. The MSD distributor came stock with the big springs installed on the mechanical advance. Those heavy springs might be too big for our application and we want the timing to go from initial to full (total timing) a little faster. Example: Total timing is measured by revving the engine to 2,500-3,500 rpm or wherever the timing stops advancing and checking the timing at full advance. In this case we wanted 35 degrees total timing. Now by reducing the spring sizes on the mechanical advance we can speed up the time it takes for the mechanical advance weights to go to full advance or total timing at 35 degrees.