Downpipe

Remove and replace the downpipe assembly connecting the exhaust manifolds to the catalytic converters on a 2005 Dodge Viper 8.3L V10, including oxygen sensor transfer.

Warnings

Tools required

Parts

• Downpipe gasket kit (manifold to downpipe) × 2 — Use OEM specification or equivalent aftermarket
• Downpipe to catalytic converter gaskets × 2 — Use OEM specification or equivalent aftermarket

Preparation

1. Ensure engine and exhaust system are completely cold to the touch
2. Park vehicle on level surface and apply parking brake
3. Place wheel chocks behind rear wheels
4. Disconnect negative battery terminal to prevent accidental starter engagement
5. Raise front of vehicle using floor jack and support securely on jack stands at manufacturer-specified lift points
6. Spray all exhaust flange bolts and oxygen sensor threads with penetrating oil and allow to soak for 15-30 minutes

Procedure

1. 1

   Access downpipe area
   From underneath the vehicle, locate the downpipe assemblies. The Viper V10 has two downpipes, one for each bank of cylinders, running from the exhaust manifolds rearward to the catalytic converters. Inspect the heat shields covering the downpipes and identify mounting hardware.
2. 2

   Remove heat shields
   Remove any heat shield fasteners securing heat shields over the exhaust piping, if equipped (verify presence and exact fastener count against the factory service manual). Set heat shields aside for reinstallation. Set heat shields aside for reinstallation. Clean mounting surfaces with wire brush if necessary.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
3. 3

   Disconnect oxygen sensors
   Locate the pre-catalytic converter oxygen sensors mounted in each downpipe. Disconnect the electrical connectors by pressing the release tab and pulling straight out. Using a 22mm (7/8") oxygen sensor socket, carefully unthread the oxygen sensors from the bungs. Turn counterclockwise and apply steady pressure. If sensors are seized, apply additional penetrating oil and allow to soak. Inspect sensor condition and threads.
   ⚠Do not allow the oxygen sensor to swing and impact against vehicle components. The ceramic element is fragile and can crack.
4. 4

   Remove downpipe-to-manifold flange bolts
   At the front connection where each downpipe mates to the exhaust manifold flange, remove the flange bolts. Remove the flange fasteners at each manifold connection (verify exact count and fastener size against the factory service manual). Work carefully as these fasteners are exposed to extreme heat cycles. If bolts are severely corroded, apply heat or additional penetrating oil as needed. Support the downpipe with one hand while removing the final bolt to prevent it from dropping.
   ⚠Flange bolts may break due to heat cycling and corrosion. Have replacement hardware available if needed.
5. 5

   Remove downpipe-to-catalytic converter flange bolts
   At the rear connection where each downpipe mates to the catalytic converter inlet flange, remove the flange bolts. Remove the flange fasteners at each catalytic converter connection (verify exact count, fastener size, and joint type — flanged, spring-loaded ball joint, or slip joint — against the factory service manual). Support the downpipe weight as you remove the final fasteners. Support the downpipe weight as you remove the final fasteners.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
6. 6

   Remove exhaust hangers
   If the downpipes are supported by rubber exhaust hangers, release them by pulling the hanger loops off the mounting brackets using a prying motion. Note the orientation for reinstallation. Some installations may not use hangers if the downpipes are fully supported by the flange connections.
   Torque spec

   Hanger Bolts20 Nm (15 lb-ft)
7. 7

   Remove downpipes
   Carefully lower each downpipe assembly from the vehicle. The downpipes may be tight against the transmission tunnel or frame rails. Rotate and manipulate as needed to clear obstructions. Remove and discard old gaskets from both manifold and catalytic converter flanges. Inspect downpipe condition for cracks, excessive corrosion, or damage.
8. 8

   Clean mating surfaces
   Using a wire brush and scraper, thoroughly clean all flange mating surfaces on the exhaust manifolds and catalytic converter inlets. Remove all old gasket material, carbon buildup, and corrosion. Ensure surfaces are flat and smooth for proper sealing. Wipe clean with shop towels.
9. 9

   Inspect oxygen sensor bungs
   Check the oxygen sensor threaded bungs in the new or existing downpipes for damage or debris. Chase threads with a tap if available, or carefully clean with a wire brush. Apply a thin coat of anti-seize compound to the threads only, avoiding the sensor tip area.
10. 10

    Install new downpipes
    Position new gaskets on the exhaust manifold flanges and catalytic converter inlet flanges. Carefully lift the new downpipe into position, aligning the flange bolt holes. Start all flange bolts by hand at both ends before tightening any. Reconnect exhaust hangers if equipped. Verify clearance around all components including chassis, driveshaft, and transmission.
11. 11

    Torque manifold flange bolts
    Apply anti-seize compound to the threads of the manifold flange bolts. Torque the 3 bolts at each manifold flange connection to specification in a star or alternating pattern to ensure even gasket compression and prevent warping.
    Torque spec

    Exhaust Flange Bolts45 Nm (33 lb-ft)
12. 12

    Torque catalytic converter flange bolts
    Torque the 3 bolts at each catalytic converter flange connection to specification in a star or alternating pattern.
    Torque spec

    Exhaust Flange Bolts45 Nm (33 lb-ft)
13. 13

    Install oxygen sensors
    Apply anti-seize compound to the oxygen sensor threads only, keeping compound away from the sensor tip. Thread each oxygen sensor into its bung by hand for several turns to ensure proper threading. Once seated, torque each sensor to specification using the oxygen sensor socket. Reconnect the electrical connectors, ensuring they click securely into place. Route wiring away from hot exhaust components.
    Torque spec

    O2 Sensor45 Nm (33 lb-ft)
14. 14

    Reinstall heat shields
    Position the heat shields over the downpipes in their original locations. Install and torque all heat shield mounting bolts to specification.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)
15. 15

    Final inspection and test
    Visually inspect all connections to ensure proper fitment and clearance. Verify all fasteners are torqued and oxygen sensor connectors are secured. Lower vehicle from jack stands. Reconnect negative battery terminal. Start engine and allow to idle. Listen and inspect for exhaust leaks at all flange connections. Check for unusual noises or vibrations. Allow engine to reach operating temperature and verify oxygen sensors are functioning by monitoring with a scan tool if available.

Reassembly

1. Installation is performed in reverse order of removal with new gaskets at all flange connections
2. Torque all fasteners to specification using a calibrated torque wrench
3. Apply anti-seize compound to all exhaust fastener threads and oxygen sensor threads

Verification

• Start engine and listen for exhaust leaks at manifold and catalytic converter flange connections - a ticking or hissing sound indicates a leak
• Visually inspect all connections while engine is running for visible exhaust smoke or gas escape
• Take vehicle for short test drive and verify no abnormal exhaust noise, vibration, or check engine light illumination
• After test drive, re-inspect all flange connections for leaks as heat cycling may reveal issues not apparent during initial cold start
• If equipped with scan tool, verify oxygen sensor readings are normal and sensors are responding to throttle changes

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