Tune-Up - Major

Complete major tune-up service for 1966 Corvette 327 V8 including ignition system overhaul, carburetor adjustment, valve lash adjustment, and replacement of all ignition components.

Warnings

Tools required

Parts

• Spark plugs (8) × 8 — AC Delco R44 or equivalent
• Distributor cap × 1 — Use OEM specification
• Rotor × 1 — Use OEM specification
• Ignition points set × 1 — Use OEM specification
• Condenser × 1 — Use OEM specification
• Spark plug wire set (8mm or 7mm) × 1 — Use OEM specification
• Distributor cap hold-down clips × 2 — Use OEM specification if worn
• PCV valve × 1 — Use OEM specification
• Air filter element × 1 — Use OEM specification
• Fuel filter (if equipped with inline filter) × 1 — Use OEM specification
• Distributor cam lubricant × 1 — High-temp distributor grease

Preparation

1. Park vehicle on level ground and engage parking brake.
2. Allow engine to cool completely if recently operated.
3. Disconnect negative battery cable.
4. Gather all tools, parts, and cleaning supplies.
5. Mark spark plug wire locations on distributor cap with tape and numbering for correct reinstallation.
6. Take photos of vacuum line routing and electrical connections for reference.

Procedure

1. 1

   Remove old spark plugs
   Remove spark plug wires by grasping the boot at the spark plug end and twisting while pulling. Never pull on the wire itself. Using the spark plug socket with extension, remove all 8 spark plugs. Keep them in order if you want to inspect for cylinder-specific issues. Inspect old plugs for fouling, abnormal wear, or incorrect heat range.
2. 2

   Inspect and clean spark plug wells
   Use compressed air or a clean rag to remove any debris from spark plug wells in the cylinder heads. Inspect plug wire boots for cracks, carbon tracking, or deterioration. Check cylinder head threads for damage or carbon buildup. Wire brush threads gently if needed.
3. 3

   Gap and install new spark plugs
   Gap new spark plugs to 0.035 inches using a wire-type gap tool. Verify gap specification for your specific application. Install plugs by hand first to avoid cross-threading, then torque to 25 ft-lb using a torque wrench. Apply a small amount of anti-seize compound to plug threads if desired, but reduce torque by 10% if doing so.
4. 4

   Remove distributor cap and rotor
   Remove the 2 spring clips or screws securing the distributor cap. Carefully lift off the cap, keeping spark plug wires attached. Remove the rotor by pulling straight up (press-fit) or removing the 2 screws (screw-type). Inspect the distributor shaft for excessive play by attempting to rock it side-to-side.
5. 5

   Replace ignition points and condenser
   Disconnect the primary wire from the points terminal and remove the condenser wire. Remove the single screw holding the condenser bracket and remove condenser. Remove the 2 screws holding the points set and remove points. Clean the breaker plate surface with electrical contact cleaner. Install new points set with 2 screws finger-tight. Install new condenser and secure with screw. Reconnect primary wire and condenser wire to points terminal.
6. 6

   Set points gap
   Rotate engine by hand using a wrench on the crankshaft pulley bolt until the distributor cam lobe opens the points to their widest position. Loosen the points hold-down screws slightly. Insert a 0.019-inch feeler gauge between the point contacts. Adjust the eccentric screw or sliding adjustment until the feeler gauge has light drag. Tighten hold-down screws and recheck gap. Apply a small amount of distributor cam lubricant to the distributor cam lobes.
7. 7

   Install new rotor and distributor cap
   Install new rotor onto distributor shaft, aligning any notches or tabs. If screw-type, secure with 2 screws. Inspect inside of new distributor cap for cracks or carbon tracking. Install new cap, ensuring it seats properly, and secure with 2 spring clips or screws.
8. 8

   Install new spark plug wires
   Install new spark plug wires one at a time to avoid misrouting. Route wires away from exhaust manifolds and moving parts. Firing order for Chevrolet 327 is 1-8-4-3-6-5-7-2 with cylinder #1 at front of driver side. Distributor rotates clockwise. Ensure each wire is fully seated in distributor cap tower and spark plug boot.
9. 9

   Replace PCV valve and air filter
   Locate PCV valve in valve cover or intake manifold. Pull old PCV valve from grommet and install new valve, ensuring it clicks or rattles when shaken (indicates working valve). Remove air cleaner wing nut and lid, replace air filter element, and reinstall lid.
10. 10

    Replace fuel filter (if equipped)
    If vehicle is equipped with an inline fuel filter (typically located along fuel line near carburetor), place rags beneath filter to catch fuel. Using two wrenches, loosen fittings on both sides of filter. Remove old filter noting direction of flow arrow. Install new filter with arrow pointing toward carburetor. Tighten fittings securely.
    ⚠Fuel will drain from lines when filter is removed. Have rags ready and ensure adequate ventilation. No smoking or open flames.
11. 11

    Adjust valve lash
    Remove valve covers by removing the bolts around perimeter. Clean gasket surfaces. Rotate engine to TDC on cylinder #1 (both valves closed, timing mark at 0 degrees). Using firing order, adjust valves using the "EO/IC" method: when exhaust valve is opening, adjust intake on paired cylinder; when intake is closing, adjust exhaust on paired cylinder. Proper lash for hydraulic lifters is typically zero lash plus 1/2 to 1 turn preload. For solid lifters, set to 0.012 inch intake and 0.018 inch exhaust hot specification. Rotate engine 360 degrees and repeat for remaining cylinders.
12. 12

    Reinstall valve covers
    Install new valve cover gaskets. Reinstall valve covers and torque bolts to 45-50 in-lb in a crisscross pattern, working from center outward. Do not overtighten as this can distort covers and cause leaks.
13. 13

    Reconnect battery and set initial timing
    Reconnect negative battery cable. Locate timing mark on harmonic balancer and timing tab on timing cover. Clean marks if necessary and mark TDC and desired timing mark with white paint or chalk. Connect timing light to cylinder #1 spark plug wire. Start engine and allow to reach operating temperature. With engine at idle and vacuum advance disconnected and plugged, aim timing light at timing marks. Initial timing should be set to approximately 4 degrees BTDC for base specification. Loosen distributor hold-down clamp and rotate distributor body to adjust timing. Tighten hold-down when correct.
14. 14

    Set dwell angle
    Connect dwell meter to negative terminal of coil and ground. Start engine and read dwell angle on meter. Dwell should be 28-32 degrees for an 8-cylinder engine with points ignition. If adjustment is needed, turn the adjustment screw inside distributor window (some models) or readjust points gap. Increasing points gap decreases dwell; decreasing gap increases dwell.
15. 15

    Adjust carburetor idle mixture and speed
    With engine at full operating temperature, locate idle mixture screws on carburetor base (typically 2 screws on front and rear). Turn both screws in gently until lightly seated, then back out 1.5 turns as a starting point. Adjust idle speed screw to achieve approximately 700 RPM in neutral (manual) or drive (automatic with wheels chocked and brake applied). Adjust each mixture screw individually for highest idle speed, then set final idle speed to specification. Lean mixture slightly by turning each screw in 1/8 turn for smooth idle with best emissions.

Reassembly

1. Double-check all electrical connections are secure and properly routed.
2. Verify all vacuum lines are connected per original routing.
3. Ensure valve covers are properly torqued and not leaking.
4. Verify distributor hold-down is tight after timing adjustment.
5. Check that air cleaner is properly secured.

Verification

• Start engine and verify smooth idle with no misfires or hesitation.
• Rev engine and verify clean acceleration with no stumbling.
• Verify timing remains stable at idle using timing light.
• Check for any vacuum leaks by listening for hissing sounds.
• Test drive vehicle to verify performance under load and at various speeds.
• After test drive, recheck timing and idle settings as they may drift slightly after heat cycling.
• Inspect for any fuel, oil, or vacuum leaks around work areas.
• Verify dwell angle remains within specification after all adjustments.

More procedures for this vehicle