Disassembly/Installation Notes for THY480 2002-2004 Nissan Altima 3.5SE Exhaust

Disconnect battery Remove air box assembly and intake tubing. Remove both rear catalytic converter pipes and rest on top of cross member out of the way. Unplug both o2 sensors by first removing harness brackets located on the side of the cylinder heads. You will then need to remove the harness from the retaining brackets located at the back of each cylinder head. Then you will need to remove each clip (usually grey in color) and the two plugs will slide apart. Remove two front o2 sensors from exhaust manifolds.
DRIVER SIDE.
Remove 10mm bolt holding the dipstick tube on and let the tube rest. (It will be necessary to loosen the manifold completely to remove the dip stick tube). It will be necessary to jack the motor up approximately 2”. Secure engine and remove four bolts securing the engine mount to the engine block. Remove exhaust manifold nuts. These will be reused with your new headers. You may then remove the entire manifold/catalytic assembly from the bottom of the vehicle.
While the engine is still raised, install header in from the bottom and secure with three nuts. Make sure you have the factory gasket and the header tight. At this point you can cut your manifold off of the catalytic converter. To do this you will need to cut 3/8” above the weld on the catalytic converter. (see photo). Clean and de-bur the inside and outside of the tube. You may now install your rear cat assembly along with front cat and position for best fit. Make sure all connections are tight for proper alignment. Tack assembly together with three or four tacks. Leave assembly mocked up and lower engine back down and secure engine mount to engine.
PASSENGER SIDE.
It will be necessary to jack the engine approximately 2”. Secure engine and remove four bolts securing the engine mount to the engine block. Remove manifolds nuts. These will be reused with your new headers. You may now remove the entire manifold/catalytic converter assembly from the bottom of the vehicle. While engine is still raised, install header in from bottom and secure with three nuts. Make sure you have the factory gasket installed and the headers tight. At this point you can cut your manifold off of the catalytic converter. To do this you will need to cut 3/8” above the weld on the catalytic converter. (see photo). Clean and de-bur the inside and outside of the tube. You may now install your rear cat assembly along with front cat and position for best fit. Make sure all connections are tight for proper alignment. Tack assembly together with three or four tacks.
Remove driver side assembly for finish welding. Use caution and do not allow the assembly to change position before you completely weld the header on. Reinstall header from the bottom and lower engine down. Torque engine mount bolts to factory spec.

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