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Have you ever wondered if the electronic ignition (EI) on your classic Mopar could be improved? With constant advancement of performance and fuel economy in mind and access to a 1975 Dodge Dart sporting an unmolested 225 slant six equipped with an operational factory electronic ignition and a dual ballast resistor (4-pin, 5-ohm resistor and 1.25-ohm resistor), we contacted Performance Distributors (901-396-5782) about the opportunity to evaluate their newly released Tri-Power Distributor, Inferno ignition coil, and LiveWires spark plug wires. Our plan was to baseline the stock Dart on a chassis dyno, and then install the high-energy ignition (HEI) distributor, coil, and plug wires and re-evaluate the performance of the new ignition parts on the slant six on a chassis dyno as well as note any changes in the drivability of the slant six on the street.

Performance Distributors has developed the Tri-Power ignition, which includes a performance-curved distributor equipped with a High-Energy Ignition (HEI) module and an Inferno ignition coil for the utilitarian slant six. The 4-Pin HEI module is a General Motors type module that works well with a Mopar. The use of the module reduces the complexity of the factory Mopar ignition wiring, provides full charging system voltage to the ignition coil, and removes the pesky ballast resistor.

To match the new Tri-Power Distributor, Performance Distributors provided a new Inferno ignition coil. The coil fits into the factory coil clamp on the passenger side of the slant six. The Inferno coil is designed to outperform all stock and aftermarket coils. The coil has been tested in extreme conditions and is designed to withstand extremely high engine bay temperatures. The higher output voltage of the Inferno coil will allow increased spark plug gaps up to .055” on the slant six.

Performance Distributors has also developed hi-performance spark plug wires called LiveWires. The spark plug wires have a durable silicone jacket and insulation, a low resistance value, and yet do not cause any radio interference due to the spiral wound core design. All of the plug wires are custom fitted and numbered for your particular application. The entire plug wire is protected by a sleeve that can withstand heat up to 1400° F. The aluminum wire separators were included at a minimum additional cost.


A Brief History of the Chrysler Electronic Ignition


With the 1971 mid-year introduction of an optional breaker-less ignition, Chrysler led the big three into the age of electronic ignition. Chrysler launched the electronic ignition on two performance-oriented engines, the 340 and the 426 Hemi. After a successful introduction, in 1971, Chrysler for the 1972 model year installed the electronic ignition on all the high-performance engines, which included the 340, the 400 with a 4bbl, and the 440, and EI was an option on the 318, the 360, and the 400 with a 2bbl engines. By 1973, the breaker-less ignition was standard on the entire family of engines offered by Chrysler, Dodge, and Plymouth. Ford and Chevrolet did not complete their move to electronic ignition for all their model lines until 1975.

Testing Performance Distributors’ Tri-Power Distributor, Inferno Coil, and LiveWires

Slanted High Energy Ignition


This is a secondary wave pattern for the factory Chrysler electronic ignition. The firing line is about 6 KV at idle (use the left scale 0-25 KV). The pattern is typical of magnetic pickup designed Chrysler EI from the 70s and 80s. The spark line is about 1/4 to 1/5 of the length of the firing line, and there are seven or more coil oscillations after the flame out in the cylinder. There is a distinctive point when the transistor turns on, during which the primary circuit is being charged. The entire process starts again with the transistor being turned off.

This is a secondary wave pattern for the HEI ignition. The firing line is about 7 KV at idle (use the left scale 0-25 KV) with the plugs gapped to .055”. The spark line is about 1/4 of the length of the firing line, and there are seven coil oscillations after the flame out in the cylinder. There is a distinct point when the transistor turns on, and the primary circuit is being charged. To ensure the coil does not over heat when saturation occurs, the internal solid-state electronics of the module begins limiting the current flow in the circuit. This is recognized by the unique bulge in the trace is known as a current limiting hump, and it is found on most HEI ignitions. The entire process starts again with the transistor being turned off.

With the Tri-Power Distributor, Inferno coil, and the LiveWires, the peak torque rose to 148 lb/ft at 2800 rpm, and the peak horsepower was up to 93 hp at 3700 rpm. Both of the peak numbers were double digit increases in performance over the baseline runs. The peak torque was up 21 lb/ft, and the peak horsepower was up 15 hp.

The HEI ignition wiring is super simple. All that is needed is to provide source voltage to the positive (+) post of the ignition coil, so the ballast resistor must be bypassed. The “B” terminal of the HEI module needs to attach to the positive (+) post of the coil, and the “C” terminal of the HEI module attaches to the negative (-) post of the coil. This setup will provide source voltage to the module (14 volts or more when the charging system is operating).

If the voltage to the HEI module is dropping below 14 volts, a relay will be necessary to prevent this from occurring. The relay will provide voltage directly to the module and coil from the AC generator. This will bypass any of the questionable 40+ year old resistance riddled wiring in the vehicle and provide the necessary 14+ volts for the module.


Wrapping it Up


Performance Distributors has developed an HEI ignition system that meets all of the needs of an automotive enthusiast. Their Tri-Power Distributor, Inferno coil, and LiveWires plug wires provide engine performance that can be measured on the tarmac and felt in the seat of the pants, provide a smoother running engine with better drivability characteristics, and achieve better fuel economy. If there is an interest in an ignition product from Performance Distributors, contact them or check them out online, get what you need for your ride, and then experience the performance and economy of a well-tuned HEI ignition powering your slant. 

-the Professor

The factory Mopar 5-pin ECU on the left was removed, and an old Mopar module was gutted, painted, and stickered to look like the original. The gutted ECU was installed, and this ECU keeps the factory look, but the ignition no longer suffers from the complex wiring and ballast problems that hampered many Mopar ignitions.

Nobody but you will know that the ballast resistor and the ignition ECU are fake. They look just like the originals, but they have been modified to no longer perform their designed tasks. The Performance Distributors’ Tri-Power distributor, which includes an HEI module is handling all the ignition requirements of the slant six.


Evaluating the Street Manors of the Distributor, coil, and plug wires


With the turn of the ignition key the HEI ignition equipped engine jumped to life; this was a normal occurrence even with the Mopar ignition with an engine that was cold, but the HEI did not miss a beat even with a hot engine. The Mopar ignition would struggle a bit more to get the engine running. In both cases, the coil should have been receiving source voltage (10.5-11.0 volts) during cranking, so the ability to start easier with the HEI ignition was likely the result of fresh plugs and to a lesser degree the increased plug gap. Once started, the slant six idled smoothly and did not seem any different than the Mopar ignition. The Dart traversed the central Pennsylvania countryside with ease, and it was observed the Dart tended to glide along with much less throttle application required to maintain the posted road speeds. Getting the Dart up to speed rapidly (if rapid is a term ever used with a slant six) was much less of a task than it had been in the past. Gaining speed to merge onto the interstate or overtake a slower vehicle on a country road was no longer a struggle for the Dart or a worry for the operator.


Prior to the Tri-Power Distributor, Inferno coil, the LiveWires, and the new plugs, the slant six averaged approximately 16 mpg, and with the new ignition components, the mpg increased to just under 19 mpg. That was a nice increase that was consistently repeatable (over only three fill-ups). The slant six seemed more spirited, had better road manners, and had an increase in fuel economy.

The 4-pin ECU and 2-pin single ballast resistor was a decent upgrade ignition from points or a 5-pin ECU ignition. Often the distributor’s centrifugal advance was more aggressive than the factory curve, and the ballast often was a lower resistance to help enhance the saturation of the ignition coil. These two points led to a higher performance ignition, but the ballast was still a concern.

This is a comparison of the factory curve (red) and the Performance Distributors’ custom-tailored curve (blue) for this specific slant six application. The custom-tailored curve outperforms the factory curve in almost all areas of the centrifugal advance, and the total advance comes in much sooner than the factory curve. A curve the meets the needs of the engine more closely will result in better performance and fuel economy.


Back on the Chassis Dyno


After a few weeks of enjoying the livelier slant six, the Dart was returned to Penn College for an addition series of three runs to verify the performance output. The Dart was strapped to the rollers and run through the same 2600 rpm to 3800 rpm range as the baseline. The engine impressively buzzed through the rpm range a full second and a half quicker than the baseline, and the results were just as impressive. The peak torque bounded to a rousing 148 lb/ft at 2800 rpm, and the peak horsepower leapt to 93 hp at 3700 rpm. Both of the peak numbers were double digit increases in performance over the baseline runs. The peak torque was up 21 lb/ft, and the peak horsepower was up 15 hp. The average torque and horsepower were also up with an average torque of 136 lb/ft and an average horsepower of 88 hp. Compared to the baseline runs, the average torque was up 15 lb/ft, and the average horsepower was up 15 hp. The performance results provided by the chassis dyno matched the butt in the seat performance experience that had been noticed during the street driving of the Dart.

The Chrysler designed location of the ignition coil by the head and below the AC generator provides most of the challenge with this ignition upgrade. There are two fasteners that hold the bracket in place, and they require some finesse to loosen. The nuts on the top of the coil are easily accessible. The installation of the Inferno coil was straight forward, and it installed just like a factory coil.


The installation of the Tri-Power Distributor is just like any other slant six distributor installation. The distributor dropped into place and the adjusting bolt was snugged before all the other components were installed. The first component to be addressed was jumping (or replacing with a wire) the 1.25-ohm ballast resistor. The 12 volts (14 volts with engine running) from ignition 1 was fed straight to the positive (+) post of the ignition coil. A 2nd wire from the ignition coil positive (+) post was then attached to the “B” terminal of the HEI module. A wire from the “C” terminal of the HEI module was attached to the negative (-) post of the ignition coil, and with those few steps the coil and the module would now receive in excess of 14 volts when the charging system was in operation with a running engine (more information in next paragraph). With a fresh set of new NGK spark plugs gapped to .055” torqued into place, and the LiveWires spark plug wires laced to their corresponding cylinders, a timing light was used to dial in the initial timing to 10 degrees BTDC, and the adjusting bolt was properly fastened. The HEI system was ready for some street duty and the reevaluation dyno runs.


It is imperative that the module receive a constant voltage of 14 volts or greater. Failure to maintain 14 volts will shorten the life of the module. If your module and the coil are not receiving 14+ volts (measured at the coil positive (+) and the battery negative (-) with the engine idling), it is time to investigate your charging system. With the engine running, place the red lead from the voltmeter to the positive (+) post of the battery and the black lead on the negative (-) post of the battery. If the battery voltage is over 14 volts, then the charging system is operating properly. If the voltage is below 14 volts, move the red lead to the B+ terminal on the AC generator (alternator). If the voltage is now in excess of 14 volts, the charging system is working, but there is a voltage drop concern between the generator and battery. To diagnose the voltage drop concern, it will be necessary to consult a factory shop manual. If there is a certainty that the charging system is in perfect operating condition but the module and coil still have a voltage that is under 14 volts, it is time to add a relay to the ignition wiring. The ignition 1 wire that was run to the positive (+) post of the ignition coil must be removed from the coil and moved to pin 86 of the relay. An 18-gauge wire from pin 85 of the relay must be routed to a good ground on the vehicle. This completes the control side of the relay.


Next run a fused (15-amp fuse) 14-gauge wire from the generator B+ post to pin 30 of the relay, and run a 14-gauge wire from pin 87 of the relay to the positive (+) post of the coil. This completes the power side of the relay circuit. The coil and the module will now receive source voltage (over 14 volts) right from the generator when the charging system is in operation.

The Tri-Power Distributor slipped into the location of the factory distributor without any difficulty. The HEI module resides in the area between the lower apron and the engine block in a similar fashion to the location of the vacuum advance canister on the factory distributor. The orange wire and the black wire are from the magnetic pickup (trigger) and they go to the HEI module. The red wire from pin “B” on the module and the black wire from pin “C” on the module attach to the positive (+) coil post and negative (-) coil post respectively.

The Inferno coil is installed in the factory location. The red wire and black wire from the HEI module are attached to the ignition coil. The LiveWires spark plug wires of cylinder 1 and 2 and the coil wire can be seen in this photo. Orange was selected for this application, but many other colors are available from Performance Distributors.

All the LiveWires are in place. A nice protective cover is shrink wrapped in place on each end of the LiveWires. The wires are labeled for the cylinder to which they go. The LiveWires are custom fitted for the application upon which they are to be installed. They fit perfectly.

The modified ballast resistor was installed on the bulkhead in place of the factory dual ballast resistor. This ballast will now pass the source voltage from Ignition 1 directly to the positive (+) side of the ignition coil.

The factory 5-pin ECU and 4-pin dual ballast resistor was found on the 1975 Dodge Dart. The ignition proved to be a decent design with the exception of the somewhat troublesome ballast resistor.


For the electronic ignition to operate, Chrysler developed a 5-pin electronic control unit (ECU) that was mounted on the firewall or the fender apron. The 5-pin designations (refer to Table 1) were pin 1: ignition 1 (key in run position), pin 2: ignition coil (negative), pin 3: 5-ohm side of ballast, and pins 4 and 5: magnetic pickup wiring (trigger).


The magnetic pickup coil replaced the points within the distributor. The magnetic pickup was mounted on the breaker-plate and was matched with a reluctor. The reluctor replaced the rotor, and similar to the rotor, the reluctor indicated each cylinder. Instead of a bump found on the rotor, the reluctor had a vane to represent each cylinder of the engine. When a vane rotated by the magnetic pickup, an AC signal was generated that was sent to the ECU. Based upon a specific signal voltage, the ECU would switch off the base of the transistor in the ECU, causing the voltage in the coil’s primary ignition windings to collapse.


The collapse of the primary circuit voltage induced a voltage into the secondary windings in the ignition coil. Due to the counter-electromagnetic force (CEMF) in the dissipating primary windings and the coil ratio between the primary and secondary windings of the coil, the induced secondary voltage was much greater than the primary voltage. The secondary windings produced a high-voltage that exited the ignition coil passing through the coil wire to the distributor, and then the voltage was passed to the spark plugs via spark plug wires. The distributor housing and vacuum advance canister remained the same as the points-type ignition. With the removal of the points, several advantages where achieved. The routine maintenance and periodic replacement of ignition parts became a thing of the past, the EI provided better timing accuracy, a fixed dwell provided better coil saturation (a “hotter” spark), and EI provided rock-solid stability for higher RPM capacity without mechanical failure (points bounce or float).

The original factory slant six distributor was chucked up in a Sun 404 Distributor machine. The factory advance curve was slow and full advance was at a very high RPM. The upper left inset shows the full centrifugal advance at 16 degrees at the camshaft or 32 degrees at the crankshaft. The lower inset shows the full advance was not achieved until 2000 rpm at camshaft speed or 4000 rpm crankshaft speed. There was so much centrifugal advance in the distributor that the initial timing was limited to top-dead-center (TDC).


While the new EI system sufficiently handled the ignition requirements of most customer vehicles, many of the ignition parts were holdovers from the points-type distributors, and thus, the ignition had an Achilles’ heel. If you have driven a ‘70s era Mopar or any Mopar that required ballast resistor in the ignition primary circuit, you may have experienced the joy of this Achilles’s heel in the form of “sneaker mode” (you get to walk because your car’s engine does not start). The ballast resistor, a positive temperature coefficient (PTC) resistor (as the temperature of the resistor goes up the resistance goes up at a linear amount), was known to fail, causing an open condition in the primary ignition circuit. With the open, there was no current flow through the ballast to the primary field windings of the ignition coil. The lack of flow in the primary windings negated the induction of the voltage into the secondary windings. Without a collapse, there would be no ignition secondary voltage to pass to the spark plugs.


Even if the ballast did not result in total failure, an operational ballast resistor tended to have a slow response time, resulting in primary field windings not being fully saturated during speedy acceleration from idle. The ballast temperature (and thus resistance) did not react quickly enough (decrease resistance) to meet the needs of the ignition. The under saturated primary field windings in the coil had a great impact upon the ignition system’s ability to ignite the air-fuel mixture in the cylinder, providing less than optimum engine performance. If you were going to do nothing more than drive your Mopar on the street, the EI system Chrysler developed was more than adequate. Just stow an additional ballast resistor into your glovebox in anticipation of the eventual failure.


If you desired more performance, could there be a better option? Chrysler offered a 4-pin ECU EI system to replace factory points type ignition and to replace the 5-pin ECU EI system. The distributor (some with a performance oriented centrifugal advance curve), 4-pin ECU, and single-ballast resistor (a 2-pin ballast resistor with a 1.25-ohm resistor or a lower resistance for greater performance) could be purchased (refer to Table 2). While the performance advance curve and lower resistance ballast resistor helped performance, the ballast resistor was still slow to react to temperature changes, and it still had potential for failure in an open condition. Could there be a way to remove the ballast to ensure performance and not have the primary ignition circuit failure?


Some time ago, some intelligent individuals discovered that the use of General Motors’ (GM) High Energy Ignition (HEI) 4-pin module could replace the Chrysler ECU and ballast resistor. Why a GM HEI on a Mopar? The GM parts are easy to obtain, the wiring is much less complex, the ignition coil gets a full source voltage (14.0 volts or greater), a “hotter” spark is generated, greater spark plug gaps are available to help ignite leaner air/fuel mixtures, and the ballast is omitted.


Performance Distributors has jumped in to provide complete HEI system for many engine applications including the slant six engine. The factory appearing Tri-Power Distributor has an HEI module attached to the housing and the Inferno ignition coil mounts in the factory location.


Baseline Dynamometer Testing

Before the Dart was strapped onto the Pennsylvania College of Technology’s Mustang chassis dyno, the factory distributor was pulled from the slant six and mocked up in a Sun 404 distributor machine. The Sun distributor machine spins the distributor shaft and the machine measures the amount of advance (centrifugal and vacuum) in degrees of camshaft rotation (double the degrees for crankshaft rotation). As the centrifugal weights sling outward with increased distributor shaft rpm, the breaker plate (and magnetic pickup) moves in proximity to the reluctor. The movement advances the breaker plate, and the spark is triggered earlier on the compression stroke as the engine rpm increases. The factory slant six provided a centrifugal advance of 16 degrees (32 degrees at the crankshaft), and the advance rate was very slow. Full advance was not achieved until 2000 rpm (4000 rpm at crankshaft) (refer to Table 3). The vacuum advance added another 9 degrees of advance (18 degrees at the crankshaft). With an initial advance of 0 degrees or top-dead-center (TDC) coupled with a centrifugal advance of 32 degrees and a vacuum advance of 18 degrees, the total advance achieved was 50 degrees of total timing. Once the advance rate and total timing information was gathered from the Sun machine, the distributor was reinstalled and the initial timing was set to TDC.

The Performance Distributors’ HEI prepped Tri-Power Distributor was set up to meet the needs of the stock slant six with a measured compression ratio of 8.45:1, a stock camshaft, and 87-octane fuel. The distributor was labeled as having 22 degrees at 3000 rpm, and when the advance curve was checked, it was dead on. The upper inset shows 11 degrees of advance at the camshaft or 22 degrees at the crankshaft, and the lower inset shows the full advance RPM at 1500 camshaft rpm or 3000 rpm at the crankshaft. The advance curve is shorter allowing for more initial advance, and it is quicker to help keep the engine’s timing optimized for performance and economy.


The ’75 Dart was secured to the Mustang chassis dyno and run through a series of three runs that established the baseline. The 75K-mile original 1bbl stock 225 slant six was run through an rpm range of 2600 rpm to 3800 rpm. The slant six output spun the rollers to a peak of 127 lb/ft of torque at 2700 rpm, and the horsepower was 78 hp at 3600 rpm (refer to Table 4). The average numbers through the rpm range were 121 lb/ft of torque and 73 horsepower. With the baseline established, it was time to install the Performance Distributor’s components and evaluate the performance on the chassis dyno.


Installing the Tri-Power Distributor, Inferno coil, and LiveWires plug wires

 To maintain the factory EI look, the 4-pin, dual ballast resistor was maintained with the HEI ignition. The 1.25-ohm resistor was ground out of the ballast, and a new wire was soldered in place of the resistor. The wire was then covered with a waterproof epoxy. The ballast resistor now passes source voltage (14 volts) from Ignition 1 “Run” to the ignition coil positive (+) post rather than dropping the voltage to 7.5 volts to 10 volts as it had previously done.

The NGK UR4 6630 spark plugs have proven to work well in the slant six, so a new set was picked up and gapped to the Performance Distributors’ recommendation of .055”. If you have the drool tube head, check for the proper plug application for that head, and remember to remove the plug gasket before installing each plug.


The Tri-Power Distributor was mounted in the Sun distributor machine prior to installation to verify the advance curve dialed in by the Performance Distributors’ employees. The distributor was marked to have 22 degrees of advance at 3000 rpm. With the distributor spun up to speed, the advance curve was dead on to the specs provided by Performance Distributors. The advance was 11 degrees at 1500 rpm (22 degrees at 3000 rpm at crankshaft) (again refer to Table 3). With the total timing set at 32 degrees, the initial timing would be set to 10 degrees before-top-dead-center (BTDC). The Performance Distributors’ distributor did not have an available vacuum advance, so the total timing would be limited to 32 degrees BTDC when cruising.



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