Exhaust Manifold And Oxygen Sensor (02S) 1: Installation

Install new exhaust manifold gasket with smooth side toward the exhaust manifold.
Install the exhaust manifold and attachment nuts.

Fig 1: Installing Exhaust Manifold
Courtesy of GENERAL MOTORS CORP.
In sequence, torque the exhaust manifold attachment nuts. The center fasteners may lose torque when the outer fasteners are tightened. Therefore, re-torque all fasteners a second time.
Torque:

Exhaust Manifold-to-Head (L24): 22 N.m (16 ft-lbs)

Exhaust Manifold-to-Head (LL0): 17 N.m (13 ft-lbs)

Exhaust manifold nut tightening sequence: See Fig 2 and Fig 3

Fig 2: Exhaust Manifold (SOHC) Tightening Sequence
Courtesy of GENERAL MOTORS CORP.

Fig 3: Exhaust Manifold (DOHC) Tightening Sequence
Courtesy of GENERAL MOTORS CORP.

NOTE: Whenever the oxygen sensor 1 is removed, coat the threads with a nickel based anti-seize such as Saturn P/N 21485279 (or equivalent). If oxygen sensor 1 is replaced, do not apply anti-seize to the new sensor. New sensors have anti-seize pre-applied. Do not use an anti-seize that contains silicone.
Connect oxygen sensor 1 harness connector. Push in until a click is heard and pull back to ensure a positive engagement.
Torque:

Sensor - Oxygen-to-Exhaust

Manifold: 45 N.m (33 ft-lbs)

Fig 4: Connecting Oxygen Sensor 1 Harness
Courtesy of GENERAL MOTORS CORP.
Install A/C compressor rear bracket and A/C compressor.
Torque:

Front/Rear Brackets-to-Head/Block: 25 N.m (19 ft-lbs)

Torque:

Compressor-to-Front Bracket: 54 N.m (40 ft-lbs)

Torque:

Compressor-to-Rear Bracket: 25 N.m (19 ft-lbs)
Raise vehicle squarely on a lift.
Install new exhaust pipe-to-manifold gasket on the studs.
Install and torque the exhaust pipe-to-manifold attachment nuts.
Torque:

Exhaust Pipe-to-Manifold: 31 N.m (23 ft-lbs)

Fig 5: Exhaust Pipe-To-Manifold Attachment Nuts And Gasket
Courtesy of GENERAL MOTORS CORP.
Slide front exhaust pipe clamp over engine block bracket and tighten clamp.
Torque:

Exhaust Pipe Clamp-to-Support

Bracket: 60 N.m (44 ft-lbs)

Fig 6: Installing Front Exhaust Pipe
Courtesy of GENERAL MOTORS CORP.
Lower vehicle and check for leaks.