All credit for the popular ignition modification created by Joe Bialy of Probetalk.com
What is the HEI modification?
You may have heard of it on forums and groups of Facebook. If your new, this mod may seem way over your head, but dont stress its quite easy.
The HEI mod is effectively using a well known, reliable and inexpensive ignition module from a different vehicle. In this case its the GM HEI ( High Energy Ignition) module that’s been used on old GM V8 engines since the 70’s. Seems backwards using 70’s technology on a 90’s vehicle? Well unfortunately these 90’s vehicles are basically using 70’s mechanical ignition technology.
How do I know if my Igniter is failing?
The most common case, is you car has been driving normally.. you get to your destination, say a store for shopping. When you return to the car minutes later, it will not start and run. For 20-60minutes of messing with it, it will not start and run, and the engine doesn’t have spark. You come back to it several hours later, and it starts and runs like there was never a problem. This will occur every time you drive it long enough for the motor to get warm.
Other times, you will be sitting at stop light, the engine will die and wont start and run again. Several hours later, it will.
Also intermittent stalling and sputtering are signs of a failing igniter.
Why does the igniter fail?
In this case, the stock igniter on these cars are built into the distributor, over time the heat and vibration damages the igniter to a point they begin to fail.
Why not just replace the stock igniter?
If you can find them, they are expensive, at-least to a point a re-manufactured distributor is the better option. They are soldered in, and internal of the distributor, witch will require dissembling the distributor and de-soldering.. all this work to have a undetermined amount of life of the distributor.
What makes the HEI the best option over getting a new or reman distributor?
A new distributor still has the same unpredictable failures as your failing distributor, it could fail the next day, a week, a month.. maybe years from when you put it in, but at some point it will leave you stranded, calling for a tow. The HEI on the other hand, while they are prone to failing, they are inexpensive, you could buy 3-4 of them for the cost of one distributor and keep them on hand, in the vehicle. They are mounted exterior of the distributor, meaning if you have a no start it issue leaving you stranded, swapping in a fresh HEI module in minutes may resolve everything.
What do I need to perform this modification?
First you will need the HEI module, This can be found at any local parts store readily available, also online.
Common part numbers for this module:
| Brand | Part # |
| GM | 10482820 |
| Niehoff | DR400 |
| Wells | DR100 |
You will also need electrical terminals and some wire, this can also be found at a local parts store, Is recommended to get heat shrinking terminals to best reduce chances of bad wire connections.
Wiring Diagrams
93-94 HEI Wiring Diagrams
With Coil and Without Coil
Below are the following diagrams for the 1993-1994 models V6 Mx6, 626 and Ford Probe. If you are going to keep the stock internal coil, you will only need an HEI unit and follow the diagram, nothing else is needed.
If you are using an aftermarket coil, you will also need a 1k ohm resistor to solder inline for the stock tachometer. Failure to use this resister may ruin the stock tachometer.
The aftermarket coil shown in the diagram is for wiring reference only. Any type or brand of coil may work, commonly the MSD blaster 3 series is most used for this application.
95-97 HEI Wiring Diagrams
With Coil and Without Coil
Below are the following diagrams for the 1995-1997 models V6 Mx6, 626 and Ford Probe. If you are going to keep the stock internal coil, you will only need an HEI unit and follow the diagram, nothing else is needed.
If you are using an aftermarket coil, you will also need a 1k ohm resistor to solder inline for the stock tachometer. Failure to use this resister may ruin the stock tachometer.
The aftermarket coil shown in the diagram is for wiring reference only. Any type or brand of coil may work, commonly the MSD blaster 3 series is most used for this application.
