Valve Cover Gaskets - Both

This procedure covers the removal and replacement of both valve cover gaskets on the 1966 Chevrolet Corvette 327ci V8, including necessary accessory removal and engine preparation.

Warnings

Tools required

Parts

• Valve cover gasket - driver side × 1 — Use OEM specification cork/rubber composite
• Valve cover gasket - passenger side × 1 — Use OEM specification cork/rubber composite
• Valve cover bolt grommets/seals × 12 — Use OEM specification rubber grommets
• Oil filler cap gasket × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and apply parking brake
2. Allow engine to cool for at least 2 hours if recently operated
3. Disconnect negative battery cable to prevent accidental starter engagement
4. Place clean shop towels or cardboard under work area to catch oil drips
5. Remove engine oil dipstick to vent crankcase pressure
6. Photograph spark plug wire routing and tag wires for proper reinstallation

Procedure

1. 1

   Remove air cleaner assembly
   Remove the wing nut securing the air cleaner lid. Lift off the lid and set aside. Remove the air filter element. Remove the air cleaner retaining hardware securing the base to the carburetor (typically a central stud or mounting nuts depending on configuration). Disconnect the crankcase vent hose and lift the assembly off. Disconnect the crankcase vent hose from the air cleaner base. Lift the air cleaner base off the carburetor and set aside. Note the location of any spacers or gaskets beneath the base.
2. 2

   Disconnect spark plug wires
   Beginning at the front of the engine, grasp each spark plug wire boot (not the wire itself) and twist gently while pulling to disconnect from the spark plug. Remove all 8 spark plug wires and route them away from the valve covers. If wires are routed through valve cover wire looms, remove the looms by unclipping or loosening mounting hardware.
3. 3

   Disconnect PCV system and breather
   On the driver side valve cover, disconnect the PCV valve from the grommet in the valve cover by pulling firmly. Disconnect the PCV hose from the carburetor base or intake manifold. On the passenger side valve cover, remove the oil filler cap and breather assembly. Some configurations have a push-in breather; others have a threaded oil filler tube that unscrews from the valve cover.
4. 4

   Remove accessory interference - driver side
   On the driver side, identify any accessories that interfere with valve cover removal. The most common is the alternator bracket or wiring harness clips. Loosen and remove any brackets or clips attached to the driver side valve cover bolts using appropriate wrenches. On some configurations, the temperature sending unit wire may need to be unclipped from the valve cover area. Do not remove the alternator itself unless absolutely necessary for clearance.
5. 5

   Remove accessory interference - passenger side
   On the passenger side, remove any accessory brackets attached to the valve cover. The most common interference is the fuel line brackets, coil mounting bracket, or oil pressure sending unit wiring. Use a 1/2" or 9/16" wrench to remove bracket bolts as needed. Support any fuel lines with wire or zip ties to prevent strain on connections.
6. 6

   Remove driver side valve cover bolts
   Using a 3/8" socket and ratchet, remove the 6 valve cover bolts from the driver side cover. The bolts are located around the perimeter of the valve cover. Remove bolts in a criss-cross pattern starting from the outer edges and working inward to prevent warping. Note the location of any bolts that also secure brackets or ground straps. Keep bolts and their grommets organized for reinstallation.
7. 7

   Remove driver side valve cover
   Once all bolts are removed, gently tap the valve cover with a rubber mallet or the palm of your hand to break the gasket seal. Carefully lift the valve cover straight up and away from the cylinder head. If the cover is stuck, use a plastic scraper or small pry bar at the gasket seam (never between the cover and head sealing surfaces) to break it loose. Avoid bending the valve cover flange. Inspect the rocker arms, pushrods, and valve train for proper condition while the cover is off.
8. 8

   Remove passenger side valve cover bolts
   Using a 3/8" socket and ratchet, remove the 6 valve cover bolts from the passenger side cover. Follow the same criss-cross pattern used on the driver side. On the passenger side, some bolts may be more difficult to access due to firewall clearance. A 3" or 6" socket extension may be necessary for rear bolts. Keep bolts and grommets organized separately from the driver side hardware.
9. 9

   Remove passenger side valve cover
   Break the gasket seal using the same technique as the driver side. Lift the passenger side valve cover straight up and away from the cylinder head. The passenger side may have tighter clearance against the firewall, requiring angling the cover slightly during removal. Inspect the valve train for proper condition.
10. 10

    Remove old gaskets and clean sealing surfaces
    Carefully remove all old gasket material from both valve cover rails and cylinder head sealing surfaces. Use a plastic or wooden scraper to avoid gouging the soft aluminum or stamped steel surfaces. Remove all traces of old cork, rubber, and RTV sealant. Clean the surfaces thoroughly with carburetor cleaner or brake cleaner and wipe with clean shop rags. Inspect the cylinder head rails for straightness and damage. Minor imperfections can be smoothed with 320-grit sandpaper. Stuff clean rags into the cylinder head openings to prevent debris from falling into the engine.
11. 11

    Clean and inspect valve covers
    Clean the inside and outside of both valve covers with brake cleaner. Remove all oil deposits, sludge, and old gasket material from the cover rails. Inspect the cover rails for warping by placing the cover on a flat surface and checking for gaps with a feeler gauge. Warpage exceeding 0.010" should be corrected by carefully straightening the cover or replacing it. Inspect the bolt holes for cracks or elongation. Clean the valve cover bolts with a wire brush and inspect threads for damage.
12. 12

    Install new gaskets
    Remove the rags from inside the cylinder heads. Position the new valve cover gasket on each valve cover (not on the cylinder head). The cork/rubber composite gaskets used on the 327 typically have locating tabs or notches that align with corresponding features on the valve cover rails. Some gaskets require a thin bead of RTV sealant at the intake manifold to cylinder head junction at the front and rear of each cover; apply sparingly only if specified by the gasket manufacturer. Install new rubber grommets on each valve cover bolt. The grommets act as seals and prevent over-compression of the gasket.
13. 13

    Install driver side valve cover
    Carefully position the driver side valve cover with gasket onto the cylinder head, ensuring the gasket remains properly seated in the valve cover rail. Align all bolt holes. Insert all 6 valve cover bolts with grommets finger-tight. Reinstall any brackets or ground straps to their original bolt locations. Once all bolts are started, tighten them in a criss-cross pattern in three stages: first to 24 in-lbs, then to 60 in-lbs, and finally to 84 in-lbs. This torque specification is typical for small block Chevrolet perimeter-style valve covers with grommets, but verify against factory documentation. Note: on the 1966 327 the valve cover bolts thread directly into the cast iron cylinder heads, not the intake manifold.
14. 14

    Install passenger side valve cover
    Position the passenger side valve cover with gasket onto the cylinder head, ensuring proper gasket alignment. Insert all 6 bolts with grommets finger-tight. Reinstall any brackets to their original locations. Tighten bolts in a criss-cross pattern using the same three-stage sequence: 24 in-lbs, then 60 in-lbs, then 84 in-lbs. Take care not to over-torque, as this is the most common cause of valve cover leaks and damaged threads in the cast iron cylinder head.
15. 15

    Reinstall PCV system and breather
    On the passenger side, install the oil filler cap and breather assembly with a new gasket if equipped. Thread or press into place as appropriate for your configuration. On the driver side, press the PCV valve firmly into the grommet in the valve cover until it seats completely. Reconnect the PCV hose to the carburetor base or intake manifold fitting, ensuring a tight connection.
16. 16

    Reinstall spark plug wires
    Refer to your photographs or wire tags. Reinstall each spark plug wire to its correct spark plug, pressing the boot firmly onto the plug until it clicks or seats completely. Route wires through any valve cover wire looms or separators. Ensure wires are not touching hot exhaust manifolds or moving engine components. Verify firing order: 1-8-4-3-6-5-7-2 with number 1 cylinder at the front driver side.
17. 17

    Reinstall air cleaner assembly
    Position the air cleaner base gasket on the carburetor. Place the air cleaner base onto the carburetor, aligning all mounting studs. Install the 3 mounting nuts and tighten securely with a 1/2" socket. Reconnect the crankcase vent hose to the air cleaner base fitting. Install the air filter element and air cleaner lid, securing with the wing nut.
18. 18

    Final inspection and reconnection
    Reinstall the engine oil dipstick. Reconnect the negative battery cable. Perform a final visual inspection to ensure all fasteners are tight, all connections are secure, and no tools or rags have been left in the engine compartment. Verify that all spark plug wires are properly routed and secured.

Reassembly

1. Torque all valve cover bolts in three progressive stages using a criss-cross pattern to prevent warping and ensure even gasket compression
2. Do not use excessive RTV sealant on gaskets; modern composite gaskets typically seal without additional sealant except at intake manifold junctions
3. Ensure PCV valve and breather are properly seated to prevent vacuum leaks and oil misting

Verification

• Start the engine and allow it to idle for 5 minutes while observing both valve covers for oil leaks
• Check around all valve cover bolt locations and gasket seams for seepage
• Listen for any unusual valve train noise that might indicate improper valve cover installation or disturbed components
• Rev the engine gently to 2000 RPM and recheck for leaks under increased crankcase pressure
• After the initial test run, shut off the engine and recheck valve cover bolt torque after the engine cools
• Verify no oil leaks after 50-100 miles of driving and retorque bolts if necessary

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