By Dr. DanteIII

Getting an HEI should be on the top of every classic Jeeper’s list. Not that there is anything wrong with the points and condenser ignition that powered every gasoline engine since somewhere around 1900, but for the most part, technology has yielded improvements in the last 100 years. Installing the HEI is a solid step about 65 years forward in ignition technology. Debuted in the early 70’s on many GM cars, the HEI was GM’s ignition of choice well into the late 80’s. This means parts are in stock and available as your and anyone else’s FLAPS. But enough history, lets get to the nuts and bolts of it.

A Little background on this particular project

There is a belief that using anything but the top of the line HEI kits will “mess up the engine.” I believe that refers to the distributor drive gear. The OEM gear is bronze or brass. The one on my new distributor is probably steel, but i didn’t really check. There is anecdotal evidence of the new drive gear being made for hardened steel, and causing premature wear on the factory cam gear. I found one account that stated the cam gear wore out in less than 50 miles. There was also a person that said they have been running the new (steel) gear for 3000 miles without incident. It was recommended that I swap the original AMC distributor gear in place of the gear on the new distributor.

To test the relative hardness of the gears, i grabbed a file from my tool box. While the AMC factory gear was easily scratched, the new gear seems to be significantly harder. Also concurrent with what i had read, the machine work on the new gear seems to be a bit rough. I then decided to swap the the gear over just to be on the safe side. The gear is secured to the distributor, for both the new and old dizzy, using a roll pin that can be easily removed with a small punch. I swapped the gear from original on to the new HEI easily. Hopefully this mean disaster averted. Even if I was going to be fine with new gear, and it was easier to spend 15 minutes swapping gears now, than 10 hours replacing the cam gear later.

The DUI brand is a proven unit, but my HEI, brand new, only cost me $99. For the Price of the DUI I could buy three of the 4WD brand. I can’t speak for longevity, but the only piece thats not a stock GM style part is the distributor base itself, so any issued arising from the cap, rotor, coil, or electronics can be remedied at a FLAPS.

Now what you’ve been waiting for!

Out with the old

In with the new!

Safety note disconnect a battery cable to avoid live wires hanging around.

Step one is easy. Remove the distributor cap by pressing down and turning the two “screws” about 1/2 way around. I chose to leave the plug wires connected, and pull the cap out of the way. I also marked a positions so I knew the orientation of the cap relative to the rotor.

Step two involves first, know where your rotor is pointing. If you can remember this, and orient the new distributor rotor in the same way, it saves you from having to worry about finding TDC on cylinder #1. The loosen the distributor hold down and seen in the picture below.

Location of distributor hold-down

Once this is loosened and out of the way, you’ve disconnected the distributor ground lead from the coil and vacuum advance hose, the old distributor should pull right our of the engine block.

Step three. Remove the cap on your new distributor so you can see the position of the rotor. Now slide the new distributor into place. Note that since the gear is helically cut, the rotor will turn slightly as the distributor engages the gear. It may take some trial and error to get your rotor back to the same position as the old one. Also be sure that distributor seats all the way down, as the oil pump is driven off of the bottom of the distributor shaft. If necessary, the oil pump can be turned using a long regular screwdriver, until everything meets up the way its supposed to.

New distributor seated in place, rotor pointing the proper direction

Step 4. Wiring. There are two ways to wire the HEI. It can be powered directly from the old coil leads, as long as you make sure to bypass the ballast resistor. ( the original coil didn’t like getting the full 12v, except when starting, the HEI NEEDS 12V power). The resistor is usually located on the firewall like so.

To make the direct power option work, all you need to do, after the resistor bypass, is connect the wires from the + side of your original coil to the “BATT” terminal on the HEI. Bam wiring done.

Wiring option two, which i chose is slightly more complicated, but also preferred for reliability and max fire power at the plugs. This option uses a relay to provide direct battery power, and the full 12-14 volts, to your new distributor.

This is fairly simple, I used a Tyco/Bosch 30/40A relay. NAPA carries an equivalent relay, but i got mine off of e-bay with a convenient pig tail. http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=330-070

Basic wiring diagram.

In this image Terminal 86 will be the wires that originally ran to the + of the coil.
Terminal 30 is a direct hot lead from your battery, I used 10Ga wire for this.
Terminal 87 is another run of 10Ga wire to the “BATT” side of the HEI.
Terminal 87a is not used, but is provided battery power when the relay is not energized.
Terminal 85 grounds the relay.

Using this method keeps the ignition from drawing excessive voltage through the small stock wiring.

Ok so you’ve got juice, and lots of it.

Step 5. Now you are going to run your new plug wires, keeping the order as from the old cap. Make sure you get at least the #1 cylinder, as you can figure out all the other after that. The AMC V8 is conveniently has each intake runner labeled with the cylinder number, making this a rather simple operation. I laid out the entire new wire set on the ground in order of legnth. The Started with the #1 cylinder and gradually worked through each one moving farther away from the distributor. This is easier than comparing lengths to your wires.

Step 6. Once you’ve got your wires in place, and your distributor situated, go back and tighten your distributor hold down. Leave it loose enough so that you canadjust the distributor, but tight enough so that the engine vibration doesn’t cause it to move on its own. Adjust the distributor to your previously established point of reference. Don’t worry if its not perfect, it will still run. Reconnect your vacuum advance hose.

Step 7 Reconnect your battery cable, plug the original vacuum advance hose (temporarily). Then start your motor, and allow it to warm up. (note: it is a good idea to verify that you have oil pressure at this point, to confirm proper oil pump engagement.) If necessary, rotate the distributor in tiny increments until a smooth idle is achieved. If your motor will not start, recheck you plug wires, and make sure all your other connections are correct.

Optional, at this point you can go and open up your spark plug gap if desired. The HEI has a significant firepower advantage over your old stock setup, and can reportedly handle plug gaps greater than 0.050″. Factory is somewhere around 0.032″. I did not do this due to time constraints, but when i get the time I will probably open it up to around 0.045-0.050″ range, just to be on the safe side. Gapping the plugs too wide will give a better idle, but at the cost of top end performance so don’t go wider than this. This is also a good time to just install new plugs, even with an HEI, i really don’t see any advantage to putting in anything exotic. Good ol’ Champions on mine.

Step 8. Set your timing, Hook your timing light up. Usually there is a lead that goes around your #1 plug wire, a wire that goes to positive battery, and a wire for ground. Start your engine, and set your timing. Factory timing is 5* BTDC, on 1970’s gasoline. It is probably safe to set it a few degrees farther advanced, expecially if your run other than regular fuel in your Jeep. Once you have your timing set, shut down the motor, and disconnect your timing light. Finally snug up the bolt for your distributor hold down. I’m sure there is a factory torque spec, but “tight” seems to work just fine.

My timing light was non functional, as i found out. I set my timing by ear. I rotated the distributor in each direction until i hear it idle a little more rough, and then picked a point that was near the middle, but slightly more retarded than advance, just to be on the safe side. This yielded no evidence or predetonation, but could have missed it due to the glasspack mufflers and the blown out exhaust gasket. As soon as possible i will set it with a light.

Step 9. Test drive your jeep. Run through the gears, and try accelerating in 2nd and 3. Listen carefully for detonation (preignition) usually characterized by a knock or ping under acceleration. If you get these symptoms, retard the timing slightly.

Initial Impressions. I haven’t had a chance to drive the jeep since my install, but the jeep seems to have better throttle response, and shorter cranking times. All in all, I am extremely pleased with my HEI, and I would reccomend it to anyone looking for a decent, easy ignition upgrade.

If you have any questions, I’m always on the ECJ5 forums (www.earlycj5.com/forums) as DrDanteIII

Discuss this how-to in our forums.

Enjoy!