This procedure covers the removal and replacement of the intermediate exhaust pipe on a 1970 AMC Rebel Machine with 390ci V8 engine, connecting the exhaust manifolds to the muffler assembly.

Warnings

Tools required

Parts

• Intermediate exhaust pipe × 1 — Use OEM specification or performance equivalent
• Exhaust flange gaskets × 2 — 2.5 inch diameter
• Exhaust pipe hangers/insulators × 2 — Replace if deteriorated
• Flange bolts and nuts × 8 — 3/8-16 grade 8

Preparation

1. Park vehicle on level surface and set parking brake firmly
2. Place wheel chocks behind rear wheels
3. Ensure exhaust system is completely cool to the touch
4. Spray all exhaust flange bolts and hanger connections with penetrating oil and allow to soak for 15-20 minutes
5. Raise front of vehicle and support securely on jack stands at frame rails behind front crossmember
6. Visually inspect exhaust system to identify all connection points and hangers for the intermediate pipe section

Procedure

1. 1

   Disconnect intermediate pipe from front exhaust manifold collectors
   Locate the flange connection where the intermediate pipe connects to the exhaust manifold collectors or header collectors. On the Rebel Machine, this is typically a ball-and-socket or two-bolt flange connection at each side. Remove the nuts or bolts securing the connection using a 9/16 inch or 15mm socket. If fasteners are seized, apply additional penetrating oil and use a box-end wrench for better leverage. Be prepared for fasteners to break; have a bolt extractor set available if needed.
2. 2

   Support intermediate pipe
   Position a jack stand or block of wood under the intermediate pipe to support its weight before disconnecting additional mounting points. This prevents the pipe from falling suddenly and causing injury or damage to other components.
3. 3

   Disconnect intermediate pipe from muffler inlet
   Move to the rear connection where the intermediate pipe meets the muffler inlet pipe. This connection is typically a slip-fit with a clamp or a flanged connection. If clamped, loosen the clamp bolts using a 1/2 inch socket. If flanged, remove the two bolts securing the connection. Separate the joint by rotating and pulling; use a pry bar if necessary to break the seal.
4. 4

   Remove exhaust hanger supports
   Identify the rubber hanger insulators supporting the intermediate pipe. The Rebel Machine typically has two hangers along the intermediate pipe section. Use a pry bar or exhaust hanger removal tool to carefully unhook the pipe hangers from the rubber insulators attached to the frame. Work carefully to avoid tearing the rubber if it will be reused.
5. 5

   Remove intermediate pipe from vehicle
   With all connections and hangers disconnected, carefully maneuver the intermediate pipe out from under the vehicle. The pipe may need to be rotated or angled to clear the transmission crossmember, driveshaft, and suspension components. Work slowly to avoid damaging brake lines, fuel lines, or other nearby components.
6. 6

   Clean flange surfaces
   Using a wire brush and scraper, thoroughly clean the flange surfaces on both the exhaust manifold collectors and the muffler inlet pipe. Remove all old gasket material, rust, and carbon deposits to ensure proper sealing with new gaskets. If flanges are severely corroded or warped, they may need to be filed flat or replaced.
7. 7

   Inspect and replace exhaust hangers
   Inspect the rubber exhaust hanger insulators for cracks, tears, or deterioration. Replace any damaged hangers to prevent excessive exhaust system movement and potential future failure. New hangers will also make installation easier.
8. 8

   Position new intermediate pipe
   Place new flange gaskets on the front manifold collector flanges and muffler inlet flange. Carefully maneuver the new intermediate pipe into position under the vehicle, routing it through the same path as the original. Align the front flanges first and start one bolt or nut at each connection to hold position.
9. 9

   Connect pipe to exhaust hangers
   Hook the intermediate pipe support tabs into the rubber hanger insulators on the frame. You may need to use a pry bar to stretch the rubber hangers enough to engage the pipe hangers. Ensure hangers are fully seated and the pipe is properly supported before tightening flange connections.
10. 10

    Install and tighten front flange connection
    Install all bolts or nuts at the front flange connection to the exhaust manifold collectors. Start all fasteners by hand to ensure proper thread engagement. Tighten in a cross-pattern to evenly compress the gasket. Without manufacturer specifications, tighten to approximately 25-30 ft-lbs, being careful not to overtighten and crack the flange or strip threads in the manifold collectors.
11. 11

    Install and tighten rear connection to muffler
    At the muffler inlet connection, ensure the slip joint is fully inserted if using a clamp-type connection, or align the flange if using a bolted connection. For clamp connections, position the clamp centered over the joint and tighten evenly. For flanged connections, install bolts and tighten in a cross-pattern to approximately 25-30 ft-lbs.
12. 12

    Verify clearances
    Visually inspect the entire intermediate pipe installation to ensure adequate clearance from the driveshaft, transmission, crossmembers, fuel lines, and brake lines. The pipe should have at least 1/2 inch clearance from all components. If necessary, loosen hangers and reposition the pipe, then re-tighten connections.

Reassembly

1. Double-check that all flange bolts are tight and that exhaust hangers are properly seated
2. Verify that no tools or parts were left under the vehicle
3. Lower vehicle from jack stands carefully

Verification

• Start engine and allow to idle. Listen for exhaust leaks at all connection points, particularly at the front and rear flanges
• With engine running, carefully feel around flange connections for escaping exhaust gases (do not touch hot components)
• Check for any contact between exhaust pipe and chassis, driveshaft, or suspension components during idle
• Take vehicle for short test drive and verify no rattles, vibrations, or exhaust smell in cabin
• After test drive, re-inspect all connections while exhaust is still warm for any signs of leaks or loosening

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