The ignition system has always been the weakest link in the combustion engine cycle. Belgian-born engineer, Jean Joseph tienne Lenoir, invented the stationary gasoline engine back in 1860 and he used a spark plug fired by a battery-powered coil device to provide ignition. In the 1880s Karl Benz came along and used a battery vibrator ignition on the first automobile. Not long after another German inventor, Werner Von Siemens invented the twin-T magneto. Then Gottlieb Daimler, another German, came up with an interesting ignition idea consisting of a heated ceramic tube that passed into the combustion chambers. Robert Bosch, yet another German came along with his oscillating low-voltage magneto, followed by the high-voltage rotary magneto. Bosch's high-voltage design became the standard magneto design. While, all of these ignition systems provided spark to the combustion chamber, none of them were very reliable, nor did they satisfy the range of the combustion engine ignition needs. Some ignition systems worked well after the engine was running, but were hard to start. Remember you were using a hand crank at the time. Some systems were good at low speeds, while other systems satisfied the engines high speed needs.
In 1906, good old American ingenuity stepped in. Charles Franklin Kettering, working out of a barn in Ohio (what is now Kettering, Ohio), invented the Kettering ignition. The Kettering ignition system was used from 1909 until the present and is what is referred to as the points ignition system.
In the points ignition system, the points were designed to create a spark as voltage arched across the opening point contacts. This constant arching caused the points to wear, thus causing the point gap to widen. This increased the current beyond that needed by the coil, causing the coil to heat up and reduce its output. While this was going on, the spark plug, because of the constant arching across the electrode, would wear and its gap would increase requiring more voltage to ignite the fuel/air mixture at a time when the ignition was sending reduced voltage. Setting and/or replacing the points and spark plugs were a scheduled practice. Every 5 - 10 thousand miles a "tune up" was required.
In 1974 General Motors, through its Delco-Remy Division, introduced the first real update in ignition systems since Kettering's 1906 invention-the High Energy Ignition system or HEI for short. The HEI system has become the mainstay in Street Rod ignition systems.
Without getting overly technical, we will attempt to describe the HEI system. In the HEI system, the points are replaced with a magnetic reluctor wheel. This star-shaped wheel rotates within a circular magnetic pole with matching points directed toward the center of the wheel. The change in magnetic flux in the reluctor and sensor assembly is detected by a winding at the base of the sensor, providing an input to a transistorized switching circuit in the ignition module. This output is then sent to a coil, similar to the points ignition system. GM elected to install the coil in the top of the distributor cap, making the HEI one piece-one big piece, often too large to fit in a street rod.
Eliminating the points, and the nagging maintenance that went with them, was a great step forward; however, the major improvement in the HEI was in the output voltage. The points ignition system put out about 20-25 thousand volts, while the stock GM HEI puts out about 35-40 thousand volts. If you have ever been bit by an HEI, you know that 35-40 volts can really sting. The increased voltage allows the spark plugs to work more efficiently as the gap increases from wear and to be less prone to fouling from oil and other contaminants in the combustion system. In addition, the higher voltage provides increased spark duration. The longer spark duration of the HEI system is instrumental in firing lean with exhaust gas recalculation (EGR) diluted fuel/air mixtures.
As good as the GM Delco-Remy HEI is, it still lags in the performance department. The HEI distributor advance curve is severely retarded, and the stock system tops out at about 4,500 rpm. Like the points system, the advance curve is controlled by weights and springs, and like the points system the springs can be changed to allow the advance to come in quicker, preferably just off idle. The curve should be about 2 degrees at 800 rpm, 6 degrees at 1,100 rpm, 10 degrees at 1,900 rpm and full at 2,200 rpm.
The HEI coil is another area of concern in a high performance environment. The stock system generates full voltage at under 4,150 rpm. Higher rpm does not allow the stock coil enough time to recharge. Early transistors used in the HEI were limited in the amount of voltage they could handle, but today's modern control modules are capable of handling higher voltage and today's performance coils are able to recharge in about 2.5 milliseconds, good enough for usable voltage to about 7,200 rpm. Remember that when upgrading an HEI system it is imperative that you match the coil and the module.
Now that we have an understanding of the HEI, let's look at the high quality aftermarket HEI systems that are now on the shelf for today's street rods. There is an array of performance, appearance, and technical options available.
Mallory
Mallory Ignition Inc., an Industry Leader in Race-Winning Performance Products during the past 75 years, recently introduced the 85 Series HEI. The unit features a CNC-machined cast 356 T-6 aluminum upper housing with a billet lower housing for lightweight durability. The unit includes Mallory's new mechanical advance mechanism and adjustable vacuum advance, and comes with a red cap and rotor with brass inserts. They're direct plug-in replacements with OE factory-type harness connectors and are available with or without Mallory's high-performance coil. You can also get them in a Race Prepped version that features locked out mechanical advance, locked out vacuum advance with chamber removed, and includes a complete advance weight and spring kit to allow for mechanical advance conversion. Mallory's HEI unit is currently available for Chevrolet engines only.
MSD
MSD has just introduced a new aluminum billet HEI for Chevrolet engines. The MSD designed HEI module and internal coil are capable of running above 9,000 RPM (as compared to 4,500 on a stock GM HEI) and provide 50-percent more spark than a stock GM HEI. The distributor also features an oversized shaft guided by a sealed ball bearing and a long sintered bushing.
MSD also offers a small-sized Chevrolet HEI for applications that do not have the space required for the large GM HEI.
In addition, the MSD catalog also features a host of HEI module and coil kits, dust covers, and other accessories to modify or upgrade OEM HEI distributors.
Pertronix, Inc.
Pertronix's entry into HEI distributors is the Flame-Thrower Street/Strip HEI. The module and the coil are engineered to perform together, to provide ignition performance without misfires up to a minimum of 7,500 rpm, almost 3,000 rpm higher than a stock HEI. The Flame-Thrower also produces 67-percent more energy in the coil with a 45-percent faster spark breakdown time. All of this delivers twice the spark of a stock HEI to the spark plug gap. The unit comes complete with a high dielectric cap (available in blue, red or black), low-resistance center coil brush, balanced rotor, and nylon hold down screws to prevent arching at higher rpm. A factory-installed adjustable vacuum canister and a mechanical advance curve kit with precision stamped weights and center plate are also included. The aluminum housing is machined from strong but light A384 alloy and is available in cast or polished versions.
Applications include small- and big-block Chevrolets, 260-455 Oldsmobiles, 301-455 Pontiacs, and 221-302 Fords.
Pertronix also has a complete line of HEI accessories, including a tune-up kit that will upgrade your stock HEI to the high performance standards of the Flame-Thrower HEI.
Speedway Motors
Bill Smith and the gang at Speedway Motors have just introduced a line of HEI distributors that meet the high quality and performance found in all Speedway Motors products. They are available for Small Block & Big Block Chevy, 302 & 351W Ford, Pontiac V-8 and Oldsmobile V-8. All Speedway Motors HEI systems are new and require a simple one-wire hookup.
