Exhaust Manifold

Remove and replace the exhaust manifolds on a 1966 Chevrolet Corvette 327ci V8, including removal of necessary accessories and gasket replacement.

Warnings

Tools required

Parts

• Exhaust manifold gasket set × 1 — Use OEM specification or Fel-Pro MS 90026
• Exhaust manifold bolts (if damaged) × 16 — 3/8"-16 x 1.25" Grade 8
• Exhaust pipe flange gaskets × 2 — Use OEM specification

Preparation

1. Park vehicle on level surface and apply parking brake. Chock rear wheels.
2. Ensure engine and exhaust system are completely cold (minimum 4 hours after last operation).
3. Disconnect negative battery cable.
4. Apply penetrating oil to all visible exhaust manifold bolts and studs. Allow to soak for several hours or overnight if possible.
5. Raise front of vehicle and support on jack stands if access from below is needed for exhaust pipe removal.

Procedure

1. 1

   Disconnect exhaust pipes from manifolds
   Working from underneath the vehicle, locate the exhaust pipe flanges at each manifold outlet. Remove the 2 bolts securing each exhaust pipe flange to the manifold. Support the exhaust pipes to prevent them from hanging on remaining connections. Separate the pipes from the manifolds and inspect the condition of the flange gaskets.
2. 2

   Remove air cleaner assembly
   Remove the wing nut securing the air cleaner lid. Lift off the lid and remove the air filter element. Disconnect the crankcase breather hoses from the air cleaner base. Remove the air cleaner mounting stud nuts and lift the entire air cleaner base assembly off the carburetor.
3. 3

   Remove spark plug wire heat shields (if equipped)
   If the vehicle is equipped with spark plug wire heat shields attached to the exhaust manifolds, remove the mounting hardware and carefully remove the shields. Set aside for reinstallation if desired.
4. 4

   Disconnect spark plug wires
   Label each spark plug wire for correct reinstallation position (cylinders 1-8). Grasp each spark plug boot firmly at the base and twist while pulling to remove from the spark plugs. Route wires out of the working area. Do not pull on the wires themselves.
5. 5

   Remove driver side manifold accessories
   For the driver side manifold, remove the dipstick tube bracket bolt from the manifold (typically one bolt). On vehicles with A/C or certain power steering configurations, it may be necessary to loosen or remove the alternator lower mounting bolt for clearance.
6. 6

   Remove driver side exhaust manifold
   Remove the 8 exhaust manifold bolts securing the driver side manifold to the cylinder head. Manifold bolts enter from the outside through the manifold flange into the cylinder head. Start with the outer bolts and work toward the center. Use a universal joint adapter for difficult angles. Once all bolts are removed, carefully lift the manifold away from the head. The manifold weighs approximately 20-25 pounds.
7. 7

   Remove passenger side manifold accessories
   For the passenger side manifold, identify any brackets or accessories attached to the manifold bolts. On some configurations, the alternator bracket or heat riser valve may be present. Remove or relocate these components as necessary for manifold removal access.
8. 8

   Remove passenger side exhaust manifold
   Remove the 8 exhaust manifold bolts securing the passenger side manifold to the cylinder head. Work in the same pattern as the driver side, starting from the outer bolts and working toward the center. Use extensions and universal joints as needed for the rear-most bolts which have limited access. Remove the manifold once all bolts are out.
9. 9

   Clean cylinder head mating surfaces
   Using a gasket scraper and wire brush, thoroughly clean all gasket material from the cylinder head exhaust port surfaces. Take care not to gouge or damage the head surfaces. Clean each port opening and remove any carbon buildup. Verify that all bolt holes are clean and free of debris. Use compressed air if available to blow out the bolt holes.
10. 10

    Inspect manifolds and hardware
    Inspect both exhaust manifolds for cracks, particularly around the bolt holes and port openings. Check the manifold mating surfaces for warping using a straightedge. Inspect all manifold bolts for thread damage, stretching, or corrosion. Replace any damaged bolts. Verify that all studs remaining in the cylinder head are tight and not damaged.
11. 11

    Install new gaskets and position driver side manifold
    Place new exhaust manifold gaskets on the driver side cylinder head, aligning the gasket ports with the head exhaust ports. The gaskets may have alignment tabs or specific orientation. Position the driver side manifold onto the head, carefully aligning all bolt holes. Support the manifold weight while starting the bolts.
12. 12

    Install and torque driver side manifold bolts
    Install all 8 manifold bolts finger-tight, ensuring the manifold is properly seated against the gaskets. Torque the bolts in a center-out spiral pattern to 25 ft-lbs in the first pass, then to final torque specification in the second pass. The factory torque specification for 327 exhaust manifold bolts is approximately 20-25 ft-lbs; use 25 ft-lbs as the final torque value for the manifold bolts on this application (verify against the GM Chevrolet shop manual).
13. 13

    Install passenger side manifold and gaskets
    Position new exhaust manifold gaskets on the passenger side cylinder head, aligning with the exhaust ports. Carefully position the passenger side manifold onto the head, supporting its weight and aligning all bolt holes. Install all 8 manifold bolts finger-tight.
14. 14

    Torque passenger side manifold bolts
    Torque the passenger side manifold bolts using the same pattern and specification as the driver side: 15 ft-lbs in the first pass, then to 25 ft-lbs final torque in a center-out pattern.
15. 15

    Reinstall accessories and exhaust pipes
    Reinstall the dipstick tube bracket to the driver side manifold. Reinstall any alternator brackets, heat shields, or other accessories removed during disassembly. Position new exhaust pipe flange gaskets at each manifold outlet. Align the exhaust pipes to the manifold flanges and install the flange bolts. Torque exhaust pipe flange bolts to 20 ft-lbs.
16. 16

    Reconnect spark plug wires and air cleaner
    Reconnect all spark plug wires to their correct spark plugs according to your previous labels (SBC firing order is 1-8-4-3-6-5-7-2). Ensure each boot is fully seated on its spark plug. Reinstall the air cleaner base assembly onto the carburetor, reconnect breather hoses, install the filter element, and secure the air cleaner lid.

Reassembly

1. Reconnect the negative battery cable.
2. Remove jack stands and lower vehicle to ground.
3. Before starting the engine, visually verify all connections are secure and no tools or parts have been left in the engine compartment.

Verification

• Start the engine and listen for any exhaust leaks at the manifold-to-head interface and exhaust pipe flanges. A slight ticking sound that disappears as manifolds heat and expand is normal for the first heat cycle.
• Allow engine to reach operating temperature and verify no exhaust leaks are present.
• Check for any unusual vibrations or exhaust odors in the cabin while idling and during test drive.
• After the first heat cycle (20-30 minutes of operation), allow engine to cool and re-torque all manifold bolts to specification to account for gasket compression.

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