3 The distributor hold-down is located below the distributor at the top of the timing chain/water pump housing. Loosen the bolt and remove the hold-down.
4 After the distributor wiring plugs are disconnected, remove the distributor by pulling it up from the engine. The rotor rotates slightly with the gear splines. Be careful not to allow dirt or items to fall into the distributor hole.
5 A side-by-side comparison of HEI and Duraspark distributors. The HEI (left) uses a much larger cap that integrates the ignition coil for less loss.
6 The old Duraspark module and its wiring can be removed and no longer used. The original wiring harness has a positive lead (usually a larger red or yellow wire) that should be marked and set aside for reuse with the new distributor.
7 Like the module, the original coil and its wiring may be removed if no longer needed. The HEI coil is capable of higher output, allowing for increased spark plug gaps, resulting in a hotter ignition and larger spark area.
8 The oil pump shaft is driven by the end of the distributor and can be seen deep within the distributor’s mount hole. It may be necessary to rotate the shaft slightly with a screwdriver to line it up with the new distributor.
9 Install the distributor in the engine, aligning the rotor in the same position as the old one that was removed. In most engines, including the AMC V-8, this aligns the key at the bottom of the distributor gear with the oil pump drive rod, allowing the distributor to drop fully in. Rotating the engine with the distributor partially installed also allows it to drop in place. In this case, place the engine back at TDC before continuing. Replace the hold-down and lightly tighten.
10 Install the HEI cap, tighten the clamps, and connect the distributor wiring harness to the cap. The HEI cap requires new spark plug wires. LiveWires spark plug wires are available for the HEI system in an AMC V-8. These wires are available in several colors and feature a protective outer mesh cover. Install the wires starting from the No. 1 position and following the 1-8-4-3-6-5-7-2 firing order.
11 With the distributor installed and lightly clamped in place, move on to getting power to the HEI. The beauty of the HEI is its integrated design, requiring only switched battery power to operate. No harness, no ignition coil wire, no mess. One of the two harness connectors that were unplugged from the old factory ignition module has a large red or yellow wire, which is the switched power source. Connect this wire to the BAT terminal in the cap of the new HEI distributor.
12 Although (technically) the distributor just needs one switched power battery wire on many AMC-era CJs, the wire from the Duraspark harness makes for hard starting due to its power being momentarily cut off during engine cranking. The Jeep’s wiring causes certain circuits to cut off during cranking to allow full power to the starter. The fix for this is using the existing starter solenoid’s bypass circuit, which is engaged during cranking, providing full power to the distributor. Splice a lead from the terminal labeled “I” into the switched power wire to the distributor.
13 The HEI delivers a higher energy spark to the spark plugs, and increasing plug gap increases ignition speed and efficiency. Most HEI systems recommend setting the plug gap at .035 to .055 inch. Using a plug gap gauge sets the gap correctly. Installing new plugs is probably a good idea but not needed unless the original plugs are old and worn.
14 Adjusting the timing is becoming a lost art form, and timing lights are becoming a thing of the past. After installing new plug wires and reconnecting the battery, attach the timing light and, with the vacuum advance hose to the distributor disconnected and plugged, start the engine. Use the timing light to observe the location of the timing mark on the harmonic balancer. Rotate the distributor to adjust to 5 degrees; when proper timing is achieved, tighten the distributor bracket.
Fine Tuning the Timing
After initial timing is set and everything is in its place, drive the Jeep, running the engine normally then make several hard acceleration runs, from both a stop and a passing style. Note the engine performance and adjust the timing if the engine seems sluggish, pings, or is hard to start. Without a timing tape on the balancer to read the exact timing, a little experimentation will find the proper timing.
Sluggish, poor performance is often a case of the timing not being advanced enough. Rotating the distributor clockwise to advance will improve performance. Do this in small intervals, followed by a driving test. If the engine shows signs of pre-ignition (pinging) or is difficult to start, the timing is likely advanced too far. Rotating backward followed by a driving test will help you to find the optimum spot.
Additional Performance Parts and Modifications
Some general performance modifications and parts are nearly universal across many engine types.
Air Filters
Reusable air filters such as ones made by K&N, AFE, and Airaid provide better filtering while increasing airflow. Driving a Jeep in off-road conditions exposes the air filter to dirtier conditions than street driving alone. Cleaning these filters more frequently ensures peak performance and longevity. For extra protection, installing a K&N pre-cleaner wrap around the air cleaner keeps larger debris off the filter element.
K&N set the standard for non-paper air filters. These filters use a gauze type material coated with a special oil to remove contaminants from air entering the engine while improving airflow. These reusable filters come in many sizes and styles.
Snorkels
Some Jeep owners install a snorkel system to prevent water from entering the engine. No direct bolt-in snorkel systems are currently available for the CJ and most are fabricated using a matching air intake plenum combined with some creative plumbing to either move the air cleaner to the outside of the Jeep at a high location, such as the windshield, or plumbing into the inside area of the Jeep’s cowl.
The interior helps keep water out when fording streams, but driving through deep water may still submerge the filter. Hydrolock is a condition experienced when water enters the engine.