Exhaust Manifold Gasket

Replace the exhaust manifold gaskets on both cylinder banks of the 327ci V8 engine to eliminate exhaust leaks and restore proper sealing.

Warnings

Tools required

Parts

• Exhaust manifold gasket set (left and right) × 1 — Use OEM specification or Fel-Pro MS90026
• Exhaust manifold studs (if damaged) × 1 — GM 3755625 or equivalent
• Exhaust pipe flange gaskets × 2 — Use OEM specification

Preparation

1. Park vehicle on level surface, engage parking brake, and place wheel chocks behind rear wheels
2. Allow engine to cool completely (minimum 3 hours after last operation)
3. Disconnect negative battery cable
4. Raise front of vehicle and support securely on jack stands at frame rails
5. Apply penetrating oil to all visible exhaust manifold nuts and exhaust pipe flange bolts, allow to soak while preparing workspace

Procedure

1. 1

   Remove spark plug wire brackets and accessories
   Remove the spark plug wire brackets attached to the exhaust manifold studs on both sides. On the passenger side, remove the dipstick tube bracket. On the driver side, disconnect any heat riser linkage if equipped. Label all wires and components for reinstallation.
2. 2

   Disconnect exhaust pipes from manifolds
   Working from underneath the vehicle, remove the 2 flange bolts connecting each exhaust pipe to its respective manifold. The 1966 Corvette uses a 2-bolt flange connection on each side. Support the exhaust pipes with wire or a stand to prevent stress on the system. Remove and discard the old flange gaskets.
3. 3

   Remove heat shields (if equipped)
   If heat shields are present on either exhaust manifold, remove the retaining bolts. Some configurations may have a shield on the passenger side near the starter; inspect to confirm whether your vehicle is equipped. Retain hardware for reinstallation.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
4. 4

   Remove left (driver side) exhaust manifold nuts
   Starting from the center and working toward the ends, remove the exhaust manifold nuts securing the left manifold to the cylinder head (verify exact count for your manifold style). Use the correct size socket for the fasteners. The center bolts are easiest to access; work outward to the front and rear. If studs turn with the nuts, grip the stud with locking pliers below the nut while loosening.
5. 5

   Remove left exhaust manifold
   Carefully remove the left exhaust manifold from the studs. The manifold may be stuck to the head due to carbon buildup. Gently tap with a rubber mallet if necessary, working around the perimeter. Be careful not to strike the manifold hard enough to crack it. Remove and discard the old gasket.
6. 6

   Remove right (passenger side) exhaust manifold nuts
   Remove the exhaust manifold nuts securing the right manifold to the cylinder head (verify exact count for your manifold style), working from center outward. Access is more restricted on the passenger side due to proximity to the frame and steering linkage. A flexible extension and ratchet are helpful for rear-most fasteners.
7. 7

   Remove right exhaust manifold
   Remove the right exhaust manifold, taking care to maneuver it past the steering linkage and frame. The manifold may need to be rotated slightly to clear obstructions. Remove and discard the old gasket.
8. 8

   Inspect and clean cylinder head mating surfaces
   Thoroughly inspect all 4 exhaust port mounting surfaces on each cylinder head for damage, warping, or cracks. Use a gasket scraper and wire brush to remove all old gasket material, carbon deposits, and corrosion. The surface must be completely clean and smooth for proper gasket sealing. Inspect all studs for damage or looseness. If any stud is damaged or pulls out of the head, it must be replaced.
9. 9

   Replace damaged studs (if necessary)
   If any exhaust manifold studs are damaged or have pulled from the cylinder head, remove the old stud completely and install a new stud. Thread the new stud into the cylinder head by hand, then tighten to specification using a stud installation tool or by double-nutting the stud. Apply anti-seize to the threads entering the cast iron head.
   Torque spec

   Exhaust Manifold Studs15 Nm (11 lb-ft)
10. 10

    Inspect exhaust manifolds
    Inspect both manifolds for cracks, particularly around the ports and bolt holes. Check the manifold mating surfaces for warping using a straightedge. Minor surface irregularities can be cleaned with a wire wheel, but warped or cracked manifolds must be replaced. Clean all carbon deposits from the manifold surfaces.
11. 11

    Install new gaskets and position left manifold
    Position the new left exhaust manifold gasket onto the cylinder head studs. The gasket print side typically faces the manifold. Install the left manifold over the studs and align it with all ports. Start all nuts by hand (verify exact count for your manifold style), threading them 3-4 turns to ensure proper thread engagement.
12. 12

    Torque left exhaust manifold nuts
    Apply a thin coat of anti-seize compound to the threads of each nut. Using a torque wrench, tighten the left manifold nuts in a center-out pattern (start with the center fasteners, then work toward front and rear alternately). Torque all nuts to specification in at least two progressive passes: first pass to 50% of final torque, second pass to full specification.
    Torque spec

    Exhaust Manifold Nuts30 Nm (22 lb-ft)
13. 13

    Install new gasket and position right manifold
    Position the new right exhaust manifold gasket onto the cylinder head studs. Carefully maneuver the right manifold into position, clearing the steering linkage and frame. Align with all ports and start all nuts by hand (verify exact count for your manifold style).
14. 14

    Torque right exhaust manifold nuts
    Apply anti-seize compound to nut threads. Torque the right manifold nuts using the same center-out pattern and progressive tightening sequence as the left side: first pass to 50% torque, final pass to specification.
    Torque spec

    Exhaust Manifold Nuts30 Nm (22 lb-ft)
15. 15

    Reinstall heat shields and accessories
    If equipped, reinstall heat shields and torque retaining bolts to specification. Reinstall spark plug wire brackets, dipstick tube bracket, and any heat riser linkage that was removed. Ensure spark plug wires are properly routed and secured away from exhaust manifolds.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)
16. 16

    Reconnect exhaust pipes
    Install new exhaust pipe flange gaskets at both manifold outlets. Raise exhaust pipes into position and install flange bolts finger-tight. Ensure pipes are properly aligned before final tightening. Tighten flange bolts securely in a cross pattern, but do not overtighten as this can distort the flange.

Reassembly

1. Reconnect negative battery cable
2. Lower vehicle from jack stands
3. Perform verification steps before returning vehicle to service

Verification

• Start engine and allow to reach operating temperature while monitoring for exhaust leaks at manifold gaskets and flange connections
• Listen for any ticking or hissing sounds that indicate exhaust leaks
• Visually inspect all manifold nuts and flange bolts to ensure none have backed out
• After initial heat cycle, allow engine to cool and re-torque all manifold nuts to specification (thermal cycling can cause slight settling)
• Check that all spark plug wires are properly secured and not contacting hot exhaust components
• Perform a test drive and recheck for leaks after 50-100 miles of operation

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