MSD Programmable Timing Computer

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The MSD Programmable Timing Computer has several features in common with the pre-programmed #121-8980 Timing Computer. Both are adjustable for 4, 6, and 8-cylinder operation and both models have a high speed retard function. The difference between the two models is that the #121-8981 has an adjustable timing curve whereas the #121-8980 is fixed. The Proframmable Computer allows you to adjust the start point, rate and total amount of the advance curve to fit your application. Three adjustments have to be made to achieve the desired timing curve. First, the idle or initial timing must be set with the Initial Timing potentiometer. This can be adjusted up to 20° from full advance (total timing). Second, the rpm level where the timing will begin advancing needs to be set. This can be set from 1,000 to 3,000 rpm. The last adjustment is the slope or how fast you want the timing to advance. The range of adjustment for this feature is from 1/2° per 1,000 rpm to 20° per 1,000 rpm. All of these timing adjustments are made with locking potentiometers located on the side of the unit. #121-8981 must be used with an MSD Ignition Control and is supplied with a 2°, 3°, and 4° module.