Distributor preparation

Thoroughly examine and clean the HEI distributor. Remove the original rotor and check the spring posts. They should not be dished by wear. Check the mechanical advance weights and make sure they move freely. Carb cleaner can be used to loosen any lightly rusted areas and will work great to clean up the components. Apply a few drops of a light oil to the moving parts. Make sure to wipe up as much excess oil as possible to keep from attracting dirt. A wire brush can be used to remove any grease or buildup found on the distributor's stem & body. Replace the old rotor with a new one. Replace the drive gear on the HEI. I suggest putting the old cap on the distributor to protect the inner components of the HEI during the gear removal process. Use a hammer & punch to drive the pin out of the drive gear and stem of the distributor. The old gear can now be removed and the new gear & pin installed. Remove the old cap.

Note: Those with pre-79 258's may need to grind or file the part of the HEI distributor shaft that drives the oil pump. This may be needed to get the HEI distributor to seat properly in the engine block. Check the fit and if needed file or grind the HEI stem until it closely matches the stock stem. It shouldn't require much if anything at all.

Installation procedures

Disconnect the battery. Unplug the wiring from the stock distributor, coil and the stock ignition module (found under the windshield washer fluid reservoir on the driver's side fender well). Remove the old coil from the jeep. The large size of the HEI distributor blocks access to the stock coil's mounting bracket. You will not be able to remove it once the HEI is installed.

Finding 0° TDC on the compression stroke:
Remove your spark plugs. Place a wine cork (or the finger of a second person) in the #1 spark plug hole. Don't force the cork into the hole, we want it to be able to come out when the piston compresses. Place a (3/4"?) wrench or socket on the vibration damper's bolt, rotate clockwise until the wine cork pops out so you now know this is the compression stroke. Note: Always rotate the engine in a "clockwise" direction as you look at the vibration damper. Continue turning until the timing mark shows 0° TDC. Make sure you have not made a complete 360° turn. If you did, this will be the exhaust stroke and you will need to start over.

Installing the HEI:
Lift the stock distributor straight out. If you have a tough time getting it out, lightly tap the base of the distributor with a hammer to loosen it.

Take the newly assembled HEI and estimate the position you would like it installed in. You determine where you want the #1 plug terminal to be. By having the engine at 0° TDC whatever terminal the rotor points to will be #1.

The stem on the HEI is what drives the oil pump. Take a long flathead screwdriver and inside of the engine block you can turn the oil pump slot so that it is going to line up with the stem on the distributor. If we put the HEI in the Jeep as is, the rotor will rotate clockwise due to the directional teeth on the drive gear and in turn will be one tooth off. To compensate for this, turn the rotor one tooth counter-clockwise before installing in the jeep. Now you can install the distributor body in any position you want, as long as the rotor points to a spark plug wire terminal on the cap. You may need to play with the position of the distributor if you have any clearance problems or if you want to position the vacuum advance unit away from the front of the vehicle. I had a minor clearance problem between the HEI cap and the engine block that was remedied by slightly rotating the distributor body. I also had to bend my dipstick (be careful if you do this) to allow the new distributor to fit. Standing in front of the jeep and looking towards the rear, my advance points to 8 o'clock and my # 1 plug terminal points to 6 o'clock. With the distributor properly seated the rotor should now be perfectly lined up with a spark plug wire terminal on the distributor cap. This terminal is now #1.Do not force the HEI into position. It should seat rather smoothly. If you experience problems then you do not have the oil pump shaft lined up or you may not be seating the drive gear properly. Note: Most HEI distributors have a notch on the body that will align with an exact position on the distributor cap... in short, there is only one position the cap can properly seat on the distributor body. Tighten down the distributor hold down clamp once you have the new HEI installed.

Note: Remember to mark the plug wire positioning on the new cap... often they are marked from the factory... by rotating the distributor and using a position not factory, it could get very confusing, especially if you take the Jeep to another mechanic who spends some time thinking position 5 is position 1... and then tears apart your timing case to “cure” the problem!

Spark plugs & spark plug wires:
Re-gap your spark plugs to .045".
Install the new spark plug wires in the proper order.

Wiring the HEI:
This is essentially a one wire hookup. The HEI distributor has two marked terminals. One is a power source and the other is for a tach signal. A simple wiring diagram

HEI distributors require 12 volts during the ignition ‘crank’ and ‘run’ positions. I used the 10-gauge red wire that fed power to my old Durapsark ignition module. If you choose this method you must make sure you use the wire that enters the ignition module and not the wire that exits. The exiting wire has resistance somewhere along the line and supplies the required 12 volts during the 'crank' position but only 9.6(?) volts during the 'run' position. Because everyone has different vehicles you may not have the same wire I used (YJ Wrangler owners see links below). A few other options for supplying the proper voltage:

1. Use the positive wire from the stock Jeep coil to trigger a 12 volt 30 amp relay. Relays are inexpensive and available at most automotive parts retailers. Wiring diagrams are included with the relays and installation is simple.

2. Run a new wire from a position in the fuse block that gets the proper voltage during the proper ignition positions.

Make sure you don't supply the new distributor with a constant 12 volts. You will eventually drain your battery and you may also have an interesting time shutting off your engine once you start it.

Those of you with factory tachometers are probably done with the wiring. My factory tach works fine even though it is not hooked up to the HEI. If you have an aftermarket tach or if you are no longer getting a signal from your existing unit then simply use the 'tach' terminal on the HEI.

Note: It is important to me that everyone understands this swap is as permanent as you would like it be. You can easily turn back at any time and return to the stock ignition setup if necessary. It is also a good idea to carry around the stock jeep ignition components as a backup.

Replace or reinstall the vacuum hose to the HEI’s vacuum advance. Use the stock vacuum port from the carb. (Ported vacuum will work best in most cases)

Timing:
Start the engine and set your timing. Mine is now set at 9 BTDC at 1600 rpm’s. Follow the specifications of your model and year. Then make fine adjustments if necessary.

Vacuum Curve for a 1985 CJ7