Related Photo Galleries
Distributor RecurveOnce you've determined the required amount of total spark lead for peak performance, you'll likely find that the distributor's centrifugal advance curve needs adjusting. The ideal method for that includes a professional-grade bench tester, but many hobbyists don't have such equipment readily available, nor is it always convenient to remove the distributor from the engine. An adjustable timing light and auxiliary tachometer can accomplish the same task while the distributor remains in the engine.After recording base timing, smoothly increase engine speed until the variable timing mark just begins to move and record that rpm point. Continue increasing engine speed until the variable timing mark quits moving, and record that timing and rpm point. You can then remove the cap and rotor (install a new timing limiter bushing) and test various advance springs and components until you find the combination that best suits your engine's spark lead requirements. Use caution when revving the engine, however, as high engine speed without a load could cause significant internal damage.