Alternator Belt

This procedure covers the inspection, removal, and replacement of the alternator drive belt on a 1970 AMC Rebel Machine with 390ci V8 engine.

Warnings

Tools required

Parts

• Alternator drive belt × 1 — Use OEM specification for 390ci V8

Preparation

1. Park vehicle on level surface and apply parking brake
2. Allow engine to cool completely if recently operated
3. Disconnect negative battery cable to prevent accidental engine start
4. Inspect new belt to verify correct size before beginning removal

Procedure

1. 1

   Inspect current belt condition
   Visually inspect the existing alternator belt for cracks, glazing, fraying, or oil contamination. Check belt tension by pressing down on the belt midway between the crankshaft and alternator pulleys with moderate thumb pressure. Proper tension should allow approximately 1/2 inch deflection. Note the belt routing path around pulleys for reference during installation.
2. 2

   Locate alternator adjustment hardware
   Identify the alternator mounting bolt at the bottom pivot point and the adjustment bolt at the top slotted bracket. The 1970 390ci V8 uses a bracket-mounted alternator on the passenger side of the engine with a slotted adjustment system.
3. 3

   Loosen adjustment bolt
   Using a 1/2 inch wrench or ratchet, loosen the alternator adjustment bolt located at the top of the alternator bracket. This bolt passes through the slotted adjustment bracket. Loosen it 3-4 full turns but do not remove completely.
4. 4

   Loosen pivot bolt
   Loosen the lower alternator pivot bolt approximately 2-3 turns. This bolt serves as the pivot point for alternator adjustment. Do not remove this bolt completely as it supports the alternator weight.
5. 5

   Push alternator toward engine
   Using hand pressure or a pry bar if necessary, push the alternator body toward the engine block to create maximum slack in the belt. The alternator should pivot on the lower mounting bolt. If the alternator does not move freely, verify both adjustment and pivot bolts are sufficiently loosened.
6. 6

   Remove old belt
   With the alternator pushed fully inward, slip the belt off the alternator pulley first, then remove it from the crankshaft pulley. If equipped with power steering or air conditioning, carefully work the belt around those components. Inspect all pulleys for damage, wear, or misalignment while the belt is removed.
7. 7

   Install new belt
   Route the new belt around the crankshaft pulley first, ensuring it seats fully in the pulley groove. Then loop the belt around the alternator pulley, keeping the alternator pushed toward the engine for maximum slack. Verify the belt is properly seated in all pulley grooves with no twists.
8. 8

   Adjust belt tension
   Using a pry bar between the alternator housing and engine block, or pulling on the alternator by hand, pivot the alternator away from the engine to create proper belt tension. Apply tension evenly to avoid cocking the alternator in its mount. Proper tension allows approximately 1/2 inch deflection when pressing firmly on the belt between pulleys with thumb pressure.
9. 9

   Tighten adjustment bolt
   While maintaining tension on the alternator with one hand or the pry bar, tighten the upper adjustment bolt firmly with the other hand. Ensure the alternator does not shift position as the bolt is tightened. The adjustment bolt should be snug but not over-torqued as it threads into the bracket slot.
10. 10

    Tighten pivot bolt
    Tighten the lower pivot bolt securely. This bolt carries the load of the alternator and belt tension, so ensure it is tight. Recheck belt tension after tightening both bolts, as the alternator may shift slightly during final tightening.
11. 11

    Reconnect battery and test
    Reconnect the negative battery cable. Start the engine and observe the belt operation. The belt should run smoothly without squealing, slipping, or excessive vibration. Check that the alternator is charging properly by observing the dashboard charge indicator light or gauge.

Reassembly

1. No disassembly beyond belt removal is required for this procedure
2. Ensure all adjustment hardware is tight before operating vehicle
3. Dispose of old belt properly according to local regulations

Verification

• With engine running, verify no belt squeal or slipping noise is present
• Check that battery charging system is functioning by observing dashboard charge indicator
• Recheck belt tension after 100 miles of operation as new belts may seat and stretch slightly
• Visually confirm belt is tracking properly in center of all pulley grooves with engine running

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