Remove and replace the intermediate exhaust pipe connecting the exhaust manifolds to the mufflers on a 1966 Chevrolet Corvette with 327ci V8 engine.

Warnings

Tools required

Parts

• Intermediate exhaust pipe × 1 — Use OEM specification or aftermarket equivalent
• Exhaust flange gaskets (manifold to intermediate pipe) × 2 — Use OEM specification
• Exhaust flange bolts and nuts × 6 — 3/8"-16 x 1" Grade 8
• Muffler inlet clamps × 2 — 2.5" exhaust clamps

Preparation

1. Park vehicle on level, solid surface and engage parking brake.
2. Place wheel chocks behind rear wheels.
3. Allow exhaust system to cool completely (minimum 2 hours after engine operation).
4. Apply penetrating oil liberally to all exhaust flange bolts, nuts, and clamp hardware. Allow to soak while preparing vehicle.
5. Raise front of vehicle with floor jack at frame rails.
6. Support vehicle securely on jack stands placed under frame rails behind front wheels.
7. Lower jack and verify vehicle stability on stands.
8. Apply additional penetrating oil to all fasteners and allow 15 minutes soak time.

Procedure

1. 1

   Remove muffler inlet connection
   Locate the slip-fit connection or clamp where the intermediate pipe enters the muffler inlet. Loosen the clamp bolt using a 9/16" socket and ratchet. If clamp is severely rusted, apply additional penetrating oil and use breaker bar. Remove clamp completely. The intermediate pipe should slide out of the muffler inlet; use twisting motion if necessary to break carbon seal.
2. 2

   Support intermediate pipe
   The intermediate pipe will now be hanging only from the front flange connection. Support the pipe weight with one hand or have an assistant hold it to prevent stress on the flange bolts during removal.
3. 3

   Remove exhaust hanger (if equipped)
   Check if the intermediate pipe has a rubber hanger supporting it mid-span. If present, use exhaust hanger removal tool or large pliers to disconnect the hanger from the frame bracket. Pull the rubber grommet off the pipe hanger rod. Some 1966 Corvettes may not have intermediate pipe hangers depending on configuration.
4. 4

   Remove front flange bolts
   At the exhaust manifold connection, identify how the intermediate pipe attaches. On the 1966 Corvette this is typically a slip-fit joint secured by a clamp rather than a bolted flange. Loosen the clamp bolt with a 9/16" socket and remove the clamp. If a bolted flange is present (aftermarket or modified system), use a 9/16" socket on the bolt heads and a 9/16" wrench on the nuts and remove all fasteners. Verify the actual connection type on your vehicle before proceeding. If fasteners are seized, apply heat carefully with propane torch to nut side only, avoiding damage to manifold gasket surface.
5. 5

   Remove intermediate pipe
   With all fasteners removed, pull the intermediate pipe rearward and downward to clear the manifold flange. Maneuver the pipe out from under the vehicle. The pipe may require rotation or angling to clear frame rails and crossmembers during removal.
6. 6

   Remove old gasket material
   Inspect the exhaust manifold flange face. Remove the old flange gasket completely using a scraper or wire brush. Clean the flange face thoroughly to ensure proper seating of the new gasket. Check flange face for warping or damage; minor surface corrosion is normal but deep pitting may cause leaks.
7. 7

   Inspect and prepare new pipe
   Compare new intermediate pipe to old pipe to verify correct length, bend angles, and flange positioning. Clean the flange face of the new pipe with wire brush. If reusing original pipe, wire brush both flange faces and inspect for cracks, especially near welds.
8. 8

   Install new flange gasket
   If the system uses a bolted flange (aftermarket/modified), position the new exhaust flange gasket onto the manifold flange so it fits snugly over the bolt holes, with any crush ring or bead facing the manifold. For the factory slip-fit/clamp joint, no flange gasket is used; instead ensure the slip joint is clean and properly seated before clamping.
9. 9

   Position intermediate pipe
   Maneuver the new or cleaned intermediate pipe into position under the vehicle. Align the front flange with the exhaust manifold flange and gasket. Insert the rear end of the pipe partially into the muffler inlet (approximately 2 inches) to hold position. The pipe may need slight manipulation to align all connection points simultaneously.
10. 10

    Install flange bolts finger-tight
    Install the 3 new flange bolts through the intermediate pipe flange and gasket into the manifold flange. Thread nuts onto bolts and tighten by hand until all bolts are finger-tight. Do not fully tighten yet. Verify gasket remains properly positioned and has not shifted during bolt installation.
11. 11

    Tighten flange bolts
    If a bolted flange connection is present, tighten the fasteners evenly in a cross pattern. Consult the factory service manual or fastener manufacturer specification for the correct torque value, as no verified factory flange-bolt torque is available for this connection. Do not overtighten, as this can warp the flange or crack the manifold. If torque wrench is unavailable, tighten firmly with ratchet until gasket is fully compressed and flange is pulled tight to manifold face. Do not overtighten as this can warp the flange or crack the manifold.
12. 12

    Connect muffler inlet
    Verify the intermediate pipe is fully inserted into the muffler inlet (minimum 2 inches overlap). Position the inlet clamp over the connection point, centered on the joint. The clamp should bridge the slip joint with approximately equal coverage on both pipe sections.
13. 13

    Tighten muffler clamp
    Tighten the muffler inlet clamp bolt using a 9/16" socket and ratchet. Tighten firmly until the clamp compresses and locks the joint securely. Tighten to the clamp manufacturer's specification (typically printed on the packaging). For a 2.5" U-bolt clamp this is commonly in the 20-30 ft-lbs range, but always follow the specific clamp maker's figure rather than a generic value. Ensure the pipe has not pulled out of the muffler during tightening.
14. 14

    Reinstall exhaust hanger
    If an exhaust hanger was present on the original pipe, reinstall it now. Insert the hanger rod into the rubber grommet and push the grommet onto the frame bracket. The hanger should support the pipe weight and prevent excessive movement, but should not pull or push the pipe out of alignment.

Reassembly

1. Visually inspect all connections to ensure flange bolts are tight and clamps are secure.
2. Check that intermediate pipe has adequate clearance from frame rails, crossmembers, and body components throughout its length.
3. Remove jack stands and lower vehicle to ground.
4. If replacing both intermediate pipes (dual exhaust), repeat entire procedure for opposite side.

Verification

• Start engine and allow to idle. Listen carefully for exhaust leaks at flange and muffler connections. A leak will produce a distinct ticking or hissing sound that increases with engine RPM.
• With engine running, carefully feel around flange connection (without touching hot surfaces) for exhaust gas escaping. A leak will produce a pulsing air stream.
• Increase engine speed to 2000 RPM and hold. Listen for any rattles or contact noises indicating the intermediate pipe is touching frame or body components.
• Perform a test drive and listen for unusual exhaust noises, rattles, or vibrations.
• After test drive and cool-down, re-check all flange bolts and clamps for tightness. Re-torque if necessary as gaskets and clamps may seat further after heat cycling.

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