Get A Small-Cap Distributor With The Power Of A Performance HEI

When it comes to performance ignitions, there has been a myriad of advancements made over the years. Case in point, how many still use or remember using dual-points distributors? These were sufficient for the time — albeit maintenance-heavy — ignition system that worked well on stock engines. However, government mandates in the ’70s demanded the OEMs deliver vehicles that offered better emissions and fuel economy.

One way to accomplish this necessitated the engine burn leaner fuel mixtures. The leaner air/fuel mixtures required greater ignition voltage and more spark to ignite the combustion process. Overcoming this challenge forced GM engineers to design a better distributor. Enter the High Energy Ignition (HEI) which effectively replaced the points-style systems that had been in service for decades.

A Big Dose Of Energy

The GM HEI distributor was a wonder of the time. No longer was an external coil needed as the HEI incorporated one in the package. Also, no voltage resistor was needed to keep the points from burning. The HEI incorporates a magnetic pick-up assembly that contains a permanent magnet, a pole piece with internal teeth, and an electronic module. The HEI works as it senses pulses emanating from the spinning distributor shaft as it rotates within the magnetic pick-up. It then provides a low-voltage digital on-off signal to the ignition module, where it is interpreted as an RPM signal. The ignition module uses this information to determine when to fire the ignition coil.

HEI distributor

The HEI cap measures 5.25-inches in diameter, whereas the Dual Power measures 4-inches. Both distributors use an internal module that is mounted underneath the reluctor assembly. While the HEI cap houses the coil, the Smaller Dual-Power distributor utilizes an external coil. The smaller-cap distributor is capable of supplying excellent spark while retaining a stock-ish appearance.

Because its reliability and the high-energy spark it delivered, it was — and still is — a staple-upgrade among many enthusiasts. These days thanks to companies like Performance Distributors, you can even find a plethora of aftermarket high-performance modules, coils, and even complete, ready-to-run HEI distributors that can be added to a high-performance engine. What’s more, these new products can help the HEI provide excellent spark energy and RPM potential exceeding 7,000 rpm.

The HEI does not come without a glaring downside, its size. While it’s tough to argue the distributor’s capabilities, many enthusiasts prefer to not have a very large distributor standing out like a sore thumb in a classic hot rod. Luckily, the folks at Performance Distributors realize this and have just what you OE-look hot rodders are wanting — the Dual Power distributor.

Customers who call in can have a distributor tuned to their engine specs. – Brian Caruth, Performance Distributors

A Smaller Package With Big Energy

“The biggest difference is size,” says Brian Caruth, of Performance Distributors.  “The DUI cap measures 5.25-inches in diameter, whereas the Dual Power measures 4-inches in diameter.” Now, this smaller cap diameter does not mean it offers less in performance.

“Both distributors use an internal module that is mounted underneath the armature/reluctor assembly,” affirms Brian. “Due to the smaller size of the Dual Power, it utilizes the Inferno 2 external coil. The Inferno 2 is rated at 45kv and has a top RPM ability of 10,000 revs. The Street/Strip DUI internal coil is rated at 50kv and has a maximum RPM output of 7,000-7,500. We have it rated at 7,000 rpm. But, if pushed to the limit, it will hit 7,500. Both coils can jump a massive plug gap of .055-inch. Also, both systems use our high-dwell Dyna-Module for increased spark duration over stock-style modules. This greatly improves throttle response and low-end performance.”

It sounds like both options are very capable units for enthusiasts, and it’s nice to know that those looking to keep a somewhat factory appearance can do so without sacrificing performance. That being said, the Dual Power — while the design does mimic the factory system — does have a few appearance aspects that make it look aftermarket. “The Dual Power has a billet aluminum housing and the DUI is cast aluminum that is polished for a high-tech, billet-like appearance,” says Brian. If you’re considering the Dual Power because of its small design but really don’t want it to stick out like a sore thumb, a light coating of a cast-gray paint will do a great job of concealing the modern dizzy.

HEI Distributor

According to Brian, both systems use a high-dwell Dyna-Module for increased spark duration over stock-style modules. This greatly improves throttle response and low-end performance.

Geared For Performance

As far as compatibility with both cast and billet camshafts, both can be ordered with gear options to coexist with the camshaft of your choice. “The DUI includes a cast-iron distributor gear, that is compatible only with hydraulic and flat tappet cams,” states Brian. “But it is available with optional gears for roller-cam compatibility. The Dual Power includes a melanized gear.”

HEI distributor

At one time, a bronze gear was required when running a billet camshaft. Now, Melonizing creates a steel distributor gear that is harder than a standard iron or bronze gear, and are compatible with both hydraulic- or solid-roller iron-gear-fitted camshafts.

A quick search of the internet lets us know that Melonite (Melonizing) is a thermochemical treatment for improving the surface properties of steel parts. This Nitriding process gives the gear an extremely hard and slick surface to prevent excessive friction and wear, as well as rust accumulation. Melonized steel distributor gears are harder than standard iron or bronze gears and are compatible with both hydraulic- or solid-roller iron-gear camshafts.

The Perfect Ignition Curve

Finally, both the DUI HEI and Dual Power units are tuned on the distributor machine for an accurate advance curve that provides maximum performance throughout the entire RPM range. “Customers who call in can have a distributor tuned to their engine specs,” affirms Brian. “Distributors that are sold through resellers are pre-tuned with a performance advance that works with stock to moderately modified engines.”

HEI distributor

Both the Dual Power and the HEI-style distributors are spun on the distributor machine to create the perfect ignition-advance curve for any engine. Customers can even call Performance Distributors and have the new distributor set up to the parameters of their engine.

What it boils down to is personal taste. Both the DUI HEI and the Dual Power units from Performance Distributors will deliver the spark your mill needs, it all comes down to whether you like a traditional, classic style or the tried-and-true HEI-style. Luckily, there is no incorrect option.

Article Sources

About the author

Randy Bolig

Randy Bolig has been working on cars and has been involved in the hobby ever since he bought his first car when he was only 14 years old. His passion for performance got him noticed by many locals, and he began helping them modify their vehicles.
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