Complete removal and replacement of the distributor assembly on a 1966 Chevrolet Corvette 327ci V8, including timing mark alignment and ignition timing verification.

Warnings

Tools required

Parts

• Distributor assembly (if replacing) × 1 — Use OEM specification or aftermarket HEI upgrade
• Distributor base gasket × 1 — Use OEM specification
• Distributor cap × 1 — Use OEM specification
• Rotor × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and apply parking brake
2. Turn ignition OFF and remove key
3. Disconnect negative battery cable to prevent accidental ignition system activation
4. Allow engine to cool if recently operated
5. Gather all tools and parts before beginning work

Procedure

1. 1

   Mark distributor position
   Using a white paint marker or chalk, mark the position of the distributor body in relation to the intake manifold. Make a second mark indicating the position of the rotor tip in relation to the distributor body. These reference marks are critical for proper reinstallation and timing.
2. 2

   Disconnect distributor wiring
   Disconnect the primary wire connector from the distributor body (single wire connector on points-type distributors). If equipped with a vacuum advance, disconnect the vacuum line from the vacuum advance canister by pulling firmly on the rubber hose. Note the vacuum port location for reassembly.
3. 3

   Remove distributor cap
   Using a flathead screwdriver, release the two spring clips securing the distributor cap. Carefully lift the cap away from the distributor body, leaving the spark plug wires attached. Move the cap and wires aside to provide clearance, ensuring wires are not strained or kinked.
4. 4

   Remove distributor hold-down clamp
   Locate the distributor hold-down clamp bolt at the base of the distributor where it meets the engine block. Using a 9/16" wrench or appropriate socket, loosen and remove the hold-down clamp bolt completely. Remove the clamp and set aside with the bolt.
5. 5

   Extract distributor from engine
   Firmly grasp the distributor body and pull straight upward with steady pressure. The distributor will rotate slightly as the helical drive gear disengages from the camshaft gear. Note the final position of the rotor as the distributor clears the block - this is the position it must return to during installation. Remove the old base gasket from the distributor mounting surface on the engine block.
6. 6

   Inspect distributor and gasket surfaces
   Examine the distributor drive gear for wear, damage, or metal debris. Check the distributor shaft for excessive play (more than 0.020" indicates worn bushings). Clean the engine block mounting surface thoroughly with a clean rag, removing all traces of old gasket material and debris. Inspect the distributor bore in the engine block for cleanliness.
7. 7

   Prepare new distributor for installation
   If installing a new or rebuilt distributor, install a new rotor onto the distributor shaft. Install a new base gasket onto the distributor housing base, ensuring it seats properly in the locating groove. Rotate the distributor shaft so the rotor points to the position noted during removal (accounting for the rotation that will occur during engagement).
8. 8

   Install distributor into engine
   Position the rotor approximately 20-30 degrees counterclockwise from your target mark (to account for gear rotation). Align the distributor body with the alignment marks made during removal. Carefully lower the distributor into the engine block bore, ensuring the drive gear engages the camshaft gear. The rotor will rotate clockwise as the gear engages; adjust your pre-position offset as needed so the rotor lands on your original position mark when fully seated. The rotor should end up pointing at your original rotor position mark when fully seated.
9. 9

   Secure distributor hold-down clamp
   Install the hold-down clamp over the distributor base and thread the clamp bolt into the engine block. Snug the bolt finger-tight only at this stage - the distributor must remain rotatable for timing adjustment. Ensure the distributor body aligns with the alignment marks made during removal.
10. 10

    Reconnect distributor components
    Reconnect the primary wire connector to the distributor body, ensuring a secure connection. Reconnect the vacuum advance line to the vacuum canister fitting, pushing the hose on firmly until seated. Reinstall the distributor cap, ensuring it seats fully onto the distributor body. Secure both spring clips completely.
11. 11

    Reconnect battery and verify operation
    Reconnect the negative battery cable. Start the engine and verify it runs. The engine should start and idle, though timing may be slightly off. Listen for unusual noises or misfiring that could indicate incorrect distributor installation or rotor position.
12. 12

    Set ignition timing
    Connect a timing light to cylinder #1 spark plug wire following the timing light manufacturer's instructions. Locate the timing tab on the front timing cover and the timing mark on the harmonic balancer. With engine at idle (500-600 RPM) and vacuum advance disconnected and plugged, loosen the distributor hold-down clamp bolt slightly. Aim the timing light at the timing marks. Rotate the distributor body clockwise to retard timing or counterclockwise to advance timing until the timing mark aligns with the initial timing specification for your specific 327 engine code (verify in the 1966 Corvette shop manual) on the timing tab. Tighten the hold-down clamp bolt to secure the distributor position.
13. 13

    Final timing verification and adjustment
    Reconnect and unplug the vacuum advance line. Rev the engine to approximately 2000 RPM and verify timing advances properly with the timing light. Return to idle and recheck base timing. The timing should remain stable at the specified initial timing value for your engine code at idle. If timing has shifted, repeat the adjustment procedure. Once satisfied, fully tighten the distributor hold-down clamp bolt.

Reassembly

1. Ensure distributor hold-down clamp bolt is fully tightened after timing adjustment
2. Verify all electrical connections are secure and vacuum line is properly attached
3. Double-check that distributor cap is fully seated with both spring clips engaged
4. Confirm no tools or rags have been left in engine compartment

Verification

• Start engine and verify smooth idle with no misfiring or hesitation
• Confirm timing light shows correct base timing at idle (4 degrees BTDC)
• Verify timing advances properly when engine RPM is increased
• Test drive vehicle to confirm normal acceleration and no backfiring or detonation
• Recheck timing after engine reaches full operating temperature
• Listen for any unusual noises from distributor area that could indicate improper installation

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