Advancements in cylinder heads, camshaft profiles, and exhaust and intake systems have provided a path to move a higher volume of air and fuel through the engine, improving the internal combustion process. Given the advancements in engine design, it's essential to have a powerful ignition system to ignite the compression stroke at the right moment for maximum power. One of the best ways to maximize ignition performance is with a good, high-energy ignition system that provides the optimal timing curve for the application.
We recently visited with the folks at Performance Distributors to learn what makes a well-designed Davis Unified Ignition (D.U.I.) high-energy distributor. We took a look at both the D.U.I. Street/Strip unit and the Chevy Tri-Power ignition unit that incorporates a smaller-diameter cap for extra firewall clearance. Besides the cool-looking products they offer with a variety of different-color caps, it's what's underneath that holds the science.
Each distributor is precision-manufactured from all brand-new parts and assembled to very close tolerances. The distributor's bottom gear is shimmed to provide between 0.025 and 0.030 inch of clearance, which helps provide a wide contact area between the distributor gear and the camshaft gear, helping ensure a strong magnetic field signal to the module.
Additionally, the module's dwell is increased about 3-6 degrees above stock, which, when combined with high-coil voltage, provides a strong and long-duration spark. With the higher available voltage, the spark-plug gaps can be increased from the traditional 0.035 inch to 0.055 inch to take full advantage of the stronger spark.
Unlike a stock HEI unit, which will often begin to misfire around 5,500 rpm, the higher-voltage D.U.I. Street/Strip units provide strong voltage supplies to 7,000 rpm. And one of the best features is that each distributor is custom-curved to match your vehicle's driving style and performance level-just provide Performance Distributors with the info. With the correctly matched distributor installed in your engine, you're ready to ignite all the power your engine can muster.
Timing Is Critical
Establishing the correct initial timing is critical to engine tuning. To do this properly you'll need a good timing light. This Performance Distributors model (PN 380000) uses two D batteries so that you do not have to source power with an extra wire from the car's electrical system. Best of all, it generates a bright strobe that is visible during daylight.