Exhaust Gasket - Front

Replace the front exhaust manifold gaskets on a 1966 Corvette 327ci V8 to eliminate exhaust leaks at the cylinder heads.

Warnings

Tools required

Parts

• Exhaust manifold gasket set (both sides) × 1 — Use OEM specification or Fel-Pro MS90026
• Exhaust manifold bolt set × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and apply parking brake. Chock rear wheels.
2. Allow engine and exhaust system to cool completely (minimum 2 hours after last operation).
3. Disconnect negative battery cable to prevent accidental starter engagement.
4. Raise front of vehicle and support securely on jack stands if working on driver side manifold (improved access from below).
5. Apply penetrating oil to all visible exhaust manifold bolts and allow to soak while preparing tools.

Procedure

1. 1

   Remove spark plug wires and heat shields
   Label and disconnect spark plug wires from the cylinders on the side being serviced (cylinders 1-3-5-7 driver side, 2-4-6-8 passenger side). Remove any heat shields or wire looms attached to or near the exhaust manifold. On the passenger side, the generator/alternator brackets may obstruct access; removal is not typically required but loosen if necessary for clearance.
2. 2

   Disconnect exhaust pipe from manifold
   Locate the exhaust pipe flange connection at the bottom of the exhaust manifold. Remove the 2 nuts securing the exhaust pipe flange to the manifold collector using a 9/16" socket. Support the exhaust pipe and carefully separate it from the manifold. The exhaust pipe gasket will likely be deteriorated; discard it.
3. 3

   Remove exhaust manifold mounting bolts
   Remove the 5 exhaust manifold mounting bolts securing the manifold to the cylinder head using a 9/16" socket and extensions. Work from center bolts outward. The rear-most bolt on either manifold has very limited access and may require a universal joint or flex head ratchet. Keep bolts organized for inspection.
4. 4

   Remove exhaust manifold
   Carefully work the exhaust manifold away from the cylinder head. The manifold may be stuck due to carbon buildup and corrosion. Gently tap with a rubber mallet if necessary, working around the perimeter. Once free, maneuver the manifold out of the engine bay. Be careful not to damage adjacent components.
5. 5

   Remove old gasket material
   Use a gasket scraper to carefully remove all old gasket material from the cylinder head exhaust port faces. Work carefully to avoid gouging the cast iron head surface. Use a wire brush to clean stubborn deposits. Clean the manifold mating surface in the same manner. Spray both surfaces with brake cleaner and wipe thoroughly with clean shop rags. The mating surfaces must be completely clean and flat for proper sealing.
6. 6

   Inspect manifold and bolts
   Inspect the exhaust manifold for cracks, particularly around the collector area and bolt holes. Check that all manifold bolt holes in the cylinder head are clean and threads are not damaged. Inspect all manifold bolts for thread damage, corrosion, or stretching. Replace any questionable bolts; original bolts from 1966 should be replaced as a precautionary measure.
7. 7

   Install new exhaust gaskets
   Position the new exhaust manifold gaskets onto the cylinder head exhaust ports. The gaskets are port-specific and have a distinct top and bottom orientation. The embossed side or printable surface typically faces the manifold. Ensure all port openings align correctly. Some gaskets have integral alignment tabs; use these to hold gaskets in position.
8. 8

   Install exhaust manifold
   Carefully position the exhaust manifold onto the cylinder head, aligning all bolt holes with the gasket and head ports. Thread all 5 manifold bolts by hand to ensure proper alignment before tightening any bolt. If bolts do not thread easily, remove manifold and verify gasket positioning.
9. 9

   Torque exhaust manifold bolts
   Tighten the exhaust manifold bolts in a center-outward pattern using a torque wrench to 15 ft-lbs in the first pass, then 20-25 ft-lbs in the final pass (verify against factory service manual). This gradual torque approach helps seat the gasket evenly and prevents warping the manifold or cracking the cast iron.
10. 10

    Reconnect exhaust pipe
    Position a new exhaust pipe gasket onto the manifold collector flange. Guide the exhaust pipe up to the manifold and align the flange bolt holes. Install the 2 flange nuts and tighten to 35 ft-lbs in a cross pattern. Ensure the pipe hangs freely without strain on the connection.
11. 11

    Reinstall accessories and spark plug wires
    Reinstall any heat shields, wire looms, or brackets that were removed. Reconnect spark plug wires to their original cylinders according to your labels. Ensure wires are properly seated on spark plugs and distributor cap terminals. Route wires away from hot exhaust components.
12. 12

    Reconnect battery and lower vehicle
    Reconnect the negative battery cable. If vehicle was raised, carefully lower from jack stands and remove wheel chocks.

Reassembly

1. If both front exhaust manifolds require service, repeat the procedure for the opposite side.
2. New exhaust gaskets may settle slightly after initial heat cycling. Re-check manifold bolt torque after the first 50-100 miles of operation.
3. Exhaust manifold bolts on small block Chevrolet engines are prone to loosening. Consider using anti-seize compound on bolt threads (not on torque-to-yield bolts if upgraded hardware is used).

Verification

• Start the engine and allow it to reach idle. Listen carefully for exhaust leaks at the manifold-to-head junction. A leaking gasket will produce a distinct ticking or puffing sound that increases with RPM.
• With engine at idle, carefully pass your hand near (not touching) the manifold gasket area. You should not feel exhaust pulses indicating a leak.
• Inspect the exhaust pipe connection at the manifold collector for leaks while engine is running.
• After a short test drive (5-10 minutes), re-inspect the manifold area for any signs of exhaust soot or discoloration indicating a leak.

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