Replace the front exhaust pipe on a 1970 AMC Rebel Machine 390ci V8, connecting the exhaust manifolds to the intermediate pipe.

Warnings

Tools required

Parts

• Front exhaust pipe assembly × 1 — Use OEM specification or Walker 52646
• Exhaust manifold flange gaskets × 2 — Use OEM specification
• Exhaust pipe flange nuts × 6 — 3/8-16 or 5/16-24 depending on application
• Intermediate pipe clamp or flange bolts × 1 — Use OEM specification
• Anti-seize compound × 1 — High-temperature rated

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 last engine operation)
4. Raise front of vehicle and support securely on jack stands at frame rails
5. Inspect exhaust system from underneath to identify all connection points
6. Spray all exhaust fasteners liberally with penetrating oil and allow 15-30 minutes to soak

Procedure

1. 1

   Disconnect front pipe from exhaust manifolds
   Locate the two exhaust manifold outlet flanges where the front pipe connects. Each manifold has a two-bolt flange connection. Remove the flange nuts using a box end wrench or socket. The fasteners will likely be 9/16 or 5/8 inch. Work the nuts back and forth if seized, applying additional penetrating oil as needed. Remove all flange bolts from both manifolds.
2. 2

   Separate front pipe from exhaust manifolds
   Once fasteners are removed, use a pry bar or hammer to carefully tap the front pipe flanges away from the manifold outlets. The old gaskets may be stuck. Work gently to avoid damaging the manifold flanges. Once separated, support the front pipe to prevent it from hanging on remaining connections.
3. 3

   Disconnect rear connection
   Locate where the front pipe connects to the intermediate pipe or muffler assembly. This may be a slip-fit connection with a clamp, or a flanged connection with bolts. If clamped, loosen the clamp bolts completely. If flanged, remove all flange bolts. The connection is typically located near the transmission crossmember.
4. 4

   Remove exhaust pipe hangers
   The front pipe may be supported by one or more rubber hangers or metal brackets. Inspect along the pipe length for any support points. Disconnect hangers by sliding the pipe hook out of the rubber isolator, or remove any bracket mounting bolts. Note the location and orientation of all hangers for reinstallation.
5. 5

   Remove front exhaust pipe
   With all connections and hangers disconnected, carefully lower and remove the front exhaust pipe from the vehicle. Maneuver it around the steering linkage, crossmember, and other undercarriage components. The pipe may be heavy and awkward; use caution to avoid dropping it.
6. 6

   Clean manifold flanges and inspect
   Use a wire brush to thoroughly clean the exhaust manifold outlet flanges, removing all old gasket material, carbon deposits, and corrosion. Check flanges for cracks, warping, or damage. Clean the mating surface on the intermediate pipe connection as well. Ensure all surfaces are flat and smooth for proper sealing.
7. 7

   Install new manifold flange gaskets
   Position new exhaust manifold flange gaskets over the manifold outlet studs or bolt holes. Ensure gaskets are oriented correctly with any embossed markings facing outward. Apply a thin coat of anti-seize compound to the exposed threads of the manifold studs or bolt holes.
8. 8

   Position new front pipe
   Carefully maneuver the new front pipe into position, aligning it first with the rear connection point to the intermediate pipe. Once rear alignment is established, align the front pipe flanges with both exhaust manifold outlets. The pipe should slide onto the intermediate pipe or align with its flange. You may need an assistant to support the pipe during positioning.
9. 9

   Install manifold flange fasteners
   Start all manifold flange nuts or bolts by hand, ensuring proper thread engagement. Install fasteners on both manifolds before tightening any. Once all are hand-started, tighten in a cross-pattern to ensure even pressure on the gaskets. Tighten firmly but avoid overtightening, which can crack the manifold flanges. Typical torque is 25-35 ft-lbs, though specific values are not available for this application.
10. 10

    Connect rear pipe connection
    At the rear connection to the intermediate pipe, ensure proper engagement of the slip joint or alignment of flanges. If a slip-fit connection, ensure the front pipe is inserted approximately 2-3 inches into the intermediate pipe. Install and tighten the clamp or flange bolts. Tighten clamp bolts evenly to compress the connection uniformly.
11. 11

    Install exhaust hangers
    Reconnect all exhaust pipe hangers and support brackets in their original locations. Ensure rubber isolators are properly seated and metal brackets are securely bolted. The exhaust system should hang evenly with adequate clearance from the vehicle body, frame, and suspension components.
12. 12

    Check clearances and alignment
    Visually inspect the entire front pipe installation, ensuring adequate clearance from the steering linkage, transmission crossmember, frame rails, and fuel lines. The pipe should not contact any component. Check that all connections are fully seated and all fasteners are tight. Verify the pipe hangs level and in proper alignment.

Reassembly

1. Apply anti-seize compound to all exhaust fastener threads to facilitate future service
2. Double-check all connection points are secure before lowering vehicle
3. Ensure exhaust hangers are properly supporting the system with no strain on connections

Verification

• Lower vehicle from jack stands and remove wheel chocks
• Start engine and listen for exhaust leaks at manifold connections and rear pipe joint
• With engine at idle, carefully feel around connection points for escaping exhaust gases (do not touch hot components)
• Observe for visible exhaust smoke escaping from connections
• Test drive vehicle and listen for any unusual exhaust sounds or rattles
• Re-inspect all connections after first 50 miles of driving and retighten if necessary

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