Remove and replace the distributor on a 1970 AMC Rebel Machine with 390ci V8 engine, including timing marks and rotor position alignment.

Warnings

Tools required

Parts

• Distributor × 1 — Use OEM specification or compatible AMC V8 distributor
• Distributor O-ring or gasket × 1 — Use OEM specification
• Distributor cap (if worn) × 1 — Use OEM specification
• Rotor (if worn) × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely if previously running
3. Disconnect negative battery cable
4. Ensure you have adequate lighting and access to engine compartment
5. If replacing distributor, verify replacement unit matches original specifications for 1970 390ci AMC V8

Procedure

1. 1

   Mark timing reference position
   Rotate the engine by hand using a breaker bar on the crankshaft pulley bolt (clockwise from front) until the number 1 cylinder is at top dead center (TDC) on the compression stroke. Verify by removing the number 1 spark plug and feeling for compression. Align the timing mark on the harmonic balancer with the 0-degree mark on the timing tab. Use white paint or chalk to mark the position of the distributor housing relative to the engine block for reference.
2. 2

   Mark rotor position
   Remove the distributor cap by releasing the two spring clips or removing the hold-down screws. Note the position of the rotor pointing toward the number 1 cylinder terminal on the distributor cap. Use white paint or chalk to mark this position on the distributor housing directly below where the rotor is pointing. This is critical for proper reinstallation timing.
3. 3

   Disconnect distributor wiring
   Disconnect the primary ignition wire from the negative terminal on the coil (usually a small wire connected to the distributor). If equipped with vacuum advance, disconnect the vacuum line from the distributor vacuum canister by pulling firmly. Label wires if necessary to ensure correct reconnection.
4. 4

   Remove distributor hold-down
   Locate the distributor hold-down clamp at the base of the distributor where it meets the engine block. Using a distributor wrench or 1/2 inch box end wrench, loosen and remove the hold-down bolt. Carefully remove the hold-down clamp, being careful not to drop it into the engine valley.
5. 5

   Remove distributor from engine
   Carefully pull the distributor straight up and out of the engine block. You may need to wiggle it gently while pulling. Note the position the rotor rotates to as the helical drive gear disengages (it will rotate slightly counterclockwise as it comes out). The distributor shaft should come out easily once the hold-down is removed. Inspect the O-ring or gasket at the base for wear.
6. 6

   Inspect distributor bore and drive gear
   Once the distributor is removed, look down into the distributor bore with a flashlight. Verify the oil pump drive shaft is still present and has not fallen down. The slot should be visible at the top. Check the distributor drive gear on the old unit for excessive wear or damage. Replace the O-ring or gasket on the new or rebuilt distributor.
7. 7

   Position new distributor for installation
   On the new or rebuilt distributor, position the rotor approximately 30 degrees counterclockwise from the mark you made for the number 1 cylinder position (accounting for gear rotation during installation). Install the new O-ring or gasket on the distributor body. Ensure the distributor body orientation matches the reference marks you made on the engine block.
8. 8

   Install distributor into engine
   Carefully insert the distributor into the bore, aligning the drive gear with the slot in the oil pump drive shaft. As you push down, the rotor should rotate clockwise approximately 30 degrees and align with your number 1 cylinder mark. The distributor should drop into place when properly aligned. If it does not seat fully, the drive gear may not be meshing with the oil pump shaft - remove and reposition slightly.
9. 9

   Verify rotor alignment and install hold-down
   Verify the rotor is pointing at the number 1 cylinder position mark you made earlier and the distributor housing reference marks align with the engine block marks. Install the hold-down clamp and bolt, snugging the bolt finger-tight only at this stage to allow for timing adjustment. Do not fully tighten yet.
10. 10

    Reconnect wiring and install cap
    Reconnect the primary ignition wire to the coil negative terminal. Reconnect the vacuum advance line to the distributor canister if equipped. Install the distributor cap, ensuring it is fully seated and the spring clips or screws are secured. Verify all spark plug wires are properly connected to the cap in correct firing order (1-8-4-3-6-5-7-2 for AMC 390).
11. 11

    Set initial timing
    Reconnect the battery negative cable. Start the engine and allow it to reach normal idle. Connect a timing light to the number 1 spark plug wire. Aim the timing light at the harmonic balancer timing marks. The initial timing for the 1970 AMC 390 should be set to approximately 5 degrees BTDC at idle with vacuum advance disconnected. Loosen the distributor hold-down bolt slightly if needed and rotate the distributor body clockwise to retard or counterclockwise to advance timing until correct.
12. 12

    Final tightening and verification
    Once timing is correctly set, hold the distributor body firmly in position and tighten the hold-down bolt securely. Recheck timing with the timing light to ensure the distributor did not move during tightening. Adjust if necessary and re-tighten. Reconnect vacuum advance line if it was disconnected for initial timing setting. Final timing with vacuum advance connected should be verified per factory specifications.

Reassembly

1. Verify all electrical connections are secure and properly routed
2. Confirm all spark plug wires are connected in correct firing order
3. Ensure distributor cap is fully seated with no cracks or carbon tracking
4. Verify distributor hold-down bolt is tight and distributor cannot rotate

Verification

• Start engine and verify smooth idle with no misfiring or hesitation
• Use timing light to confirm ignition timing is set to factory specification (approximately 5 degrees BTDC initial, check service manual for exact specification)
• Rev engine and verify timing advances smoothly with no hesitation
• Test drive vehicle and confirm normal acceleration and performance with no pinging or detonation under load
• Recheck timing after test drive to ensure distributor has not moved

More procedures for this vehicle