[Excaliber]

The MSD distributors ship from the factory with TWO heavy silver springs. These 'stock' springs do not allow much mechanical advance until you reach pretty high rpm. Perhaps as much as 4000 or so.

On the MSD web site you will find 'charts' and 'graphs' that show you WHAT springs to use to get advance at varying rpms. It also shows what 'stop bushing' to use to limit the max advance allowed. Typically there is a BLUE and a BLACK 'stop bushing'. One allows something like 25 degrees max advance, the other only about 18 degrees.

HOW FAST and at WHAT RPM the advance BEGINS and finally reaches MAX is determined by the various springs or combination of springs. For instance I would recommend the black stop bushing with ONE heavy silver spring and ONE light silver spring. This will give you about 18 degrees total and max advance will be reached around 2800-3000 rpm. Advance will BEGIN around 1500.

BASE timing of 18 PLUS mechanical advance of 18 equals a TOTAL advance of around 36. Possibly a bit to much, but it's almost impossible to 'dial it in' to exact numbers without sacraficing something some where. Like poor idle because the base timing is to low, or a lag in throttle response at lower rpm, but runs great at high rpm. Always a trade off some where.

The distributor must be removed and partially disassembled to replace the 'stop bushing'. Your in pretty deep here if you don't understand 'distributor basics'. You don't really need a distributor machine, you DO need to understand HOW the MSD springs, weights and stop bushings work. Without that a machine would be a waste of time anyway.

Shoot for (feel free to chime in here guys):
Begin advance at 1800 - 2000 rpm, end max advance at 3000 - 3200 rpm. Replace bushings and springs as required to hit that target, GRAPHED on the MSD web site.