![]() ![]() Long dwell times are used with inductive ignitions to fully charge, or saturate, the coil. Dwell time is the amount of time the primary circuit is complete (points closed). ![]() Generally, this was set at 30 to 32 degrees. The key adjustment for points was to measure the dwell time, which was the length of time, in degrees, that the points were closed. According to ACCEL, you should not use the clear dielectric grease on these modules (like MSDs Spark Guard) since this is actually an insulator type of grease that will act as a heat transfer barrier, which could lead to trouble.Īnother function the module performs is electronic control of the dwell circuit. This grease creates a better heat transfer path between the module and the distributor body so that the module tends to run cooler. The key to reducing heat buildup in the module is to use the special white grease supplied with new modules on the mounting side of the module. This is especially true at idle since the energy remains in the module (since little is needed at idle), which adds to the heat problem. The heat can eventually build up inside the distributor, melt the internal circuits, and destroy the module. The problem with higher amperage is heat. Some of the more high-performance aftermarket modules can draw as much as 7.5 to 8 amps of power. Better GM performance modules increase this current to around 5.5 amps. Generally, stock HEI modules are current-limited to about 4 amps. The beauty of an HEI is that even stock, it applies much more spark energy than a points-type ignition. However, these higher pressures require more spark voltage and current in order to ensure complete combustion. Increased horsepower and torque are a direct result of higher cylinder pressures. ![]() This additional power ensures more complete combustion at both idle and at wide open throttle. More power applied across the primary circuit of the coil means the coil can apply greater spark energy to the spark plugs. With an electronic module, an HEI can safely operate at much higher current loads. While voltage is reduced, the resistors main function is to reduce current, since points cannot handle more than about 2 amps of primary current without drastically reducing operating life. ![]() One of the misunderstood aspects of points ignition systems is that the ballast resistor (or resistor wire as used in most GM points-type ignitions) just limits voltage. Since charging-system voltage is applied directly to the distributor, the module acts as a current limiter on the primary side of the ignition system. The combination of the right module and coil are the key elements to a high-performance HEI distributor. Today, there are several aftermarket high- performance modules and coils that can be added to a stock GM HEI distributor to give it excellent spark energy and rpm potential up to 7,000 rpm. This was true of the early-model distributors, but it didnt take GM long to modify the modules and coils to offer greater spark energy at higher engine speeds. All you have to do to run this system is to apply a straight 12 volts to the distributor and youre ready to run.Įarly HEIs gained a reputation for giving up above 5,000 rpm, so many enthusiasts avoided them. This larger cap also offered space to position the coil, making the HEI distributor self-contained. Since this system produces more voltage and amperage output, it demanded a larger-diameter cap to prevent voltage crossfire inside the distributor cap. An HEI distributor is still an inductive-discharge ignition, but it exchanges the points for a solid-state electronic switching device called a module. In the mid-∧0s, leaner mixtures for emission reasons demanded greater voltage and more spark energy to initiate combustion. General Motors engineers designed the original HEI system to replace the points ignition that had been around for decades. This month, we thought wed investigate the advantages of high-performance inductive systems like the High Energy Ignition (HEI). Last month we looked into the differences between inductive-discharge and CD ignition systems. There are plenty of killer ignition systems that could probably weld sheetmetal, but those monster capacitive-discharge (CD) systems arent necessary for a typical street engine. Ignition systems dont make horsepower, but a weak ignition can cost you power if it cant get the combustion process started. But even the ultimate in heads, compression, cam, and the rest wont make power if you cant light the fire. High performance is all about horsepower. ![]()
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