Back in the day, point-triggered ignition system tune-ups were routine and happened roughly every 12,000 miles, along with a set of spark plugs and an ignition timing adjustment. These days, we’re so far removed from the tune-up protocol that we don’t even think about them anymore. Tune-ups are something we never think about because they’re required every 50,000-100,000 miles on distributorless ignition systems (DIS) with platinum tip spark plugs. Spark plugs and ignition coils have become life-of-the-engine components, though it is best they be replaced every 50,000-100,000 miles.
Chevrolet’s High Energy Ignition (HEI) from the Delco-Remy Division of General Motors was first offered in 1974 on production cars, though in very limited numbers. In 1975, HEI became standard on all GM vehicles. As with most ignition systems, HEI went through its share of refinements before it went away altogether at the dawn of the new millennium. It tended to falter above 5,000 rpm, which earned it no points with performance buffs. As GM refined HEI and the aftermarket got on board it only got better to where it became an industry standard. It became the best factory ignition system of its time.
The upside to HEI is how well it works and how easily it can be adapted to the Chevy classics. All you need is a switched power lead (ignition switch in the On position) and the rest becomes easy. The real beauty of the GM HEI distributor is its longer ignition coil dwell time that can deliver greater ignition current to the spark plugs at high rpm. The HEI’s integrated ignition coil in the distributor cap makes it the most compact ignition system in history. No external ignition coil to sweat out. There are some firewall interference issues with some vehicles, but not all. Otherwise, HEI drops right into any vintage Chevy small- or big-block without breaking a sweat.
Originally, the HEI system was fitted with a four-pin module. By 1978, it had a five-pin unit. Seven and eight-pin modules were more a computer-controlled element that came around in the 1980s. By the late 1980s, the writing was on the wall; HEI was in its twilight. It was ultimately replaced with distributorless ignition, better known as “coil-on-plug” ignition.
If you’re running an HEI system on your vintage Chevy, you’re only just beginning years and years of faithful service once you get this integrated ignition system installed in your vintage Vette because it is so reliable. We’re going to take an already terrific electronic ignition system and show you how to get even more from it via a PerTronix ignition module, cap and integral ignition coil.
We’re working with Ted Granger of Ted’s Carburetor Shop in Lancaster, California, north of Los Angeles in the vast Antelope Valley. Ted has witnessed thousands of these Delco HEI ignition systems and knows how to get them back on the beam. He stresses the use of PerTronix ignition components because these parts have been tested extensively and used reliably by thousands of users through the years. And, as long you follow the instructions to the letter, you will never have to worry about a breakdown. Vette
PerTronix, Summit Racing Equipment and Corvette Central have set us up with everything we’re going to need to get this HEI back in operation. Ted has done all the prep work, including mediablasting the distributor housing and the removal of all of the old components.
Ted’s Carburetor Shop managed to source these HEI bushings from a trusted source because he does so many of them. Corvette Central is a good source for conventional Delco point-triggered distributor bushings, which it has in stock.
Ted has temporarily installed the reluctor in order to properly seat the main bushing and get it flush for the C-clip, which will retain the reluctor. This groovy bushing driver is available from Corvette Central.
The bottom bushing gets seated with a bushing driver just like Ted did the main bushing. These bushings call for a nice gentle love tap until they are seated. Strike the bushing too harshly and you may shatter the distributor housing.
Once the main bushing is seated, Ted removes the reluctor C-clip, which was installed as a reference. The reluctor has to be removed to install the vacuum advance.
The Hall effect reluctor shown here is what takes the place of conventional ignition points, which were never employed in an HEI ignition, but you get the idea.
Here’s the PerTronix Flame-Thrower HEI module, which is the brains of this operation. It processes ignition coil saturation while the reluctor (not pictured) acts as a switch, like ignition points do. What makes it better than stock is the ability to handle high rpm.
Ted loads up this lubrication pocket with high-temperature wheel bearing grease, available from Summit Racing Equipment. Ted tells us he has been using wheel bearing grease for shaft and bushing lubrication for years without consequence. It gets hot as hell in there and it flows into the bushings and shaft.
This nylon washer, which is placed over the grease, keeps the lubrication where it belongs. There’s also a felt washer that goes on top of the nylon piece.
The fully adjustable vacuum advance unit is installed next.
The reluctor is reinstalled and tied to the vacuum advance rod. Ted stresses getting this right because if you overlook this step you will not have spark advance under acceleration.
Ted has his own approach to vacuum and centrifugal advance tuning. He fabricates this vacuum advance limiter from a wire connector and installs it as shown. Ted tells us he has run into excessive spark advance with HEI and older Delco ignitions. This limiter keeps vacuum advance under control.
Next is this C-clip, which keeps the reluctor stable and where it belongs.
Heat is a very destructive element, especially with electronics. It can cause ignition failure. Ted applies Super Lube dielectric compound to the PerTronix module’s mounting surface as a heat barrier.
The distributor shaft and centrifugal advance mechanism have been assembled and checked for freedom of movement. Ted has applied a light film of grease between the two components.
Ted has a regimen to limiting centrifugal advance as rpms increase. He has found over the years that Delco ignitions tend to roll in too much spark advance as rpms increase. He installs this roll pin limiter (arrow) to limit total timing. The roll pin has to be cut down to size to prevent it from colliding with ignition components beneath the advance unit.
The distributor bushings and shaft have been lubricated with wheel bearing grease. Grease gives the shaft and bushings a running start when the distributor is installed and the engine fired. Once in operation, engine oil will take care of lubricating the bushings and shaft.
At the bottom end, you’re going to want to shim the shaft and driven gear to where you get just the right amount of shaft endplay.
Ted has a supply of shim kits (available from Summit Racing Equipment) that allows him to adjust the shaft endplay. You can get away with 0.015-inch endplay. However, we’ve seen unmolested HEI distributors with as much as 0.060-inch endplay without consequence. Ideally, you will keep the endplay to around 0.020- to 0.030-inch.
Our PerTronix HEI has 0.020-inch endplay, which is fine.
Once shaft endplay has been set, install the distributor driven gear and roll pin as shown. Flat tappet camshafts get an iron driven gear. Roller tappet cams call for a bronze, steel or composite gear, which are all available from Summit Racing Equipment.
Ted applies dielectric compound to the module’s contact surfaces and installs the PerTronix Flame-Thrower module.
We’re on the home stretch of our HEI build, with only the centrifugal advance mechanism of flyweights and return springs remaining to be installed.
This is the mechanical (centrifugal) advance mechanism that employs these flyweights, which swing outward as rpm increases to advance rotor indexing and spark timing. Ted’s job as a tuner is to keep total spark timing at 36 degrees BTDC (before top dead center) at 3,000 rpm. Each tune depends upon how the engine will be operated.
Ted’s roll pin limiter keeps spark timing conservative and from getting out of control. Maximum advance occurs when the flyweight mechanism hits the stop and cannot advance any further. This approach to limiting spark advance works for Ted, but it doesn’t always work for everyone.
Ted puts the Delco HEI on his Sun distributor machine and dials in the timing. As he predicted, his limiter keeps total timing safe with a maximum spark advance of 36 degrees BTDC at 3,000 rpm. All timing should be in by 3,000 rpm.
The PerTronix distributor rotor is installed next and properly indexed.
PerTronix provides everything you’re going to need in a distributor cap and coil. The cap comes preassembled and ready to go. As you can see, the HEI’s internal coil is built into the cap, eliminating a coil lead. PerTronix distributor caps all have brass terminals for good continuity.
Because Ted’s Carburetor Shop is very meticulous, they will go through an ignition again and again to make sure everything is right. Redundant inspection followed by tuning on a distributor machine confirms everything is what it should be.
Photography by Jim Smart