Untruth: If you decide to eliminate the vacuum advance module you have to phase the rotor in the distributor. In effect, the HEI housing actually becomes a heat sink for the module. Actually, the silicone transfers the heat produced by the module to the distributor housing. Untruth: The silicone grease you place under an HEI module is designed to insulate the module from heat. It is utilized to help the module transfer the heat it develops to the distributor housing. The dielectric grease placed under a module is not there to protect the module from heat. distributors are oil-impregnated and extremely durable. “Internally, the bronze bushings utilized in Performance Distributor’s D.U.I. ![]() Truth: “There is no benefit to a billet distributor housing in terms of increasing performance - castings are stable and straight,” according to Steve. Untruth: A billet distributor housing is far superior to a cast piece. The spark has to travel a longer path of resistance.” You can also lose a small amount of spark intensity when you run a coil wire to an external oil-filled coil. The solid epoxy eliminates the possibility of leaks. This epoxy dissipates heat more efficiently than oil-filled coils. An HEI coil also runs cooler because it is encapsulated in thermal epoxy. The lower amperage draw actually results in a much cooler running HEI coil. Compare that to an external, oil-filled coil that draws roughly six amps, and there is no way it can get as hot when working properly. “First, HEI coils only draw two to three amps. Truth: “This is probably the oldest HEI distributor myth of all,” Steve quips. Untruth: Since an HEI distributor coil is mounted in the cap and is covered, it can overheat? This is not true as an HEI coil generates less heat than a traditional oil-filled “can” coil. One common misconception says the HEI’s coil can get hot, shortening its lifespan since it’s covered. The benefit of a wider plug gap is a more complete burn of the fuel mixture.” This firing ability also allows the use of wider spark plug gaps. “Today, we make high-output modules and coils that saturate fast enough to fire consistently at high RPM. Truth: “This myth is only true when the comparison is to a stock HEI distributor,” says Davis. ![]() Untruth: A long-running rumor that is often told relays that an inductive ignition - like an HEI - is not as good for use in high-performance engines as a capacitive discharge (CD) ignition. With Steve’s help, we have compiled the following most-common misconceptions about the ignition and the truths that need to be told. We wanted his input to debunk some of the more popular rumors and innuendo. To get some solid information you can store in your noggin, we reached out to Steve Davis of Performance Distributors. In fact, if you would like to read a little more about troubleshooting an HEI distributor, click here. Because of that, I thought maybe it would be a good time to clear the fog so to speak. Compounding that is the fact the internet affords anyone with an opinion a worldwide venue to spout what they think is true. Like many parts and products offered to consumers, there always seems to be untruths and misinformation that get spread like wildfire. Unfortunately, enthusiasts are never satisfied with OE applications. When used in OE applications, these changes proved to be the perfect solution. ![]() It didn’t take GM long to rectify the situation by modifying the modules and coils to offer increased spark energy at higher engine speeds. Unfortunately, the units were infamous for not delivering a solid spark at engine speeds above 5,000 rpm. ![]() However, early HEI distributors proved to be less than reliable in high-performance applications and got a bad reputation. The control module’s function is to provide the same ignition pulse as the breaker points previously found in a points and condenser system. The HEI distributor consists of a control module and a magnetic pickup inside the housing that replaces the previously used contact points and condenser. The seven- and eight-pin modules are used on early computer-controlled engines that use fixed-timing distributors. The extra pin is connected to a knock sensor. It was an early attempt at electronically controlling ignition timing. The five-pin module was introduced in 1978. (From right to left) The four-pin module was used on carbureted engines with a traditional vacuum and centrifugal advance. When discussing a factory-stock HEI, the module is probably the most misunderstood piece of the puzzle.
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