One of the most important features of the MSD Pro-Billet Distributors is the adjustable mechanical advance assembly. The mechanical advance, sometimes referred to as centrifugal advance, allows you to accurately and easily modify the advance curve to match your specific application. MSD engineers have spent many hours at the dyno controls and in our labs perfecting this great distributor feature.
A variety of timing curves can be achieved simply by changing the advance springs and stop bushing. The stop bushing determines the amount of mechanical advance that can be achieved. Each distributor is equipped from the factory with the blue (21°) bushing installed with five other bushings included; Red allows 28°, Silver 25°, Green 23°, Purple 19° and Black for 18°.
The springs determine the rate, or how fast the advance occurs. Each distributor comes with two heavy silver springs installed which give the curve the slowest advance rate. There are also two sets of springs with different tensions included; blue and light silver, which can be mixed and matched to achieve a variety of advance rates.
The charts to the left illustrate the variety of ignition timing curves you can achieve by simply changing the springs and stop bushing.