Installation

I installed the header in 2 pieces. It may be easier to pre-assemble it and install it as a unit.

Some nuts/bolts may be easier to reach from above.

Use care when handling the 02 sensor

Wrap the header prior to installation to avoid scratches such as these

Basically on the TSX the installation boils down to this.

Stock Exhaust Manifold Removal

1. Pull your TSX into your work location. This is preferably a clean and flat concrete surface.
2. Pop and prop the hood. If the engine is hot, allow the motor to cool. You can speed up this process by aiming a good sized fan at the motor. (I just rest my plastic-bodied fan directly on top of the motor and fire it directly down)
3. Remove the factory heat shield from the exhaust manifold. There are 3 bolts (12mm) securing it to the upper portion of the manifold. the lowermost bolt is a bit of a stretch to reach - you may have more success getting at it from below. Fortunately I was able to reach it with my air-powered socket wrench (air tools sure are handy sometimes).
4. With a 14mm socket and a breaker bar (use a short extension if you have clearance issues with the chassis brace), loosen (but don't fully remove) the 3 bolts and 2 nuts that hold the OEM exhaust manifold in place
5. Set the parking brake and chock the rear wheels. If you don't have access to a lift, use a good floor jack to raise the front of the car (there is a jacking point centered about 12" aft of the front bumper under the car). If using a floor jack, after raising the car about 10-12" off the floor, place jackstands underneath the jacking points on the sides of the car and lower it onto the jackstands.
6. Put on some safety glasses, then crawl underneath the car with your breaker bar, a socket wrench, a crescent wrench, a small plastic bowl to keep track of the parts that you will be removing and replacing, and 12mm and 14mm sockets. It's probably a good idea to take some socket extensions with you too.
7. Using the crescent wrench (or spanner, if you prefer), loosen the 02 sensor, which you will find just on the left side of the header immediately fore of the flex pipe. Remove the 02 sensor and then use a zip tie or something to secure it out of the way while you remove the header.
8. Remove the (3) 14mm nuts securing the manifold to the catalytic converter.
9. Remove the bolt that secures the exhaust manifold bracket to the engine block.
10. Remove the 3 bolts and 2 nuts that secure the upper portion of the exhaust manifold to the cylinder head.
11. Separate the lower portion of the exhaust manifold from the rubber hanger (near the catalytic converter)
12. Pull the manifold away from the catalytic converter while supporting the upper portion. A helper from above may be useful.
13. Pull the upper portion of the exhaust manifold away from the cylinder head (and clear of the 3 bolts protruding from the head), and then carefully drop it down from the car.

DC Sports Header Installation

1. Inspect the original exhaust manifold gasket and replace it if it is damaged.
2. I should have thought of this earlier myself, but to protect the finish of the header, wrap the header in some old T-Shirts or towels and then secure with masking tape or elecrical tape, being extremely careful not to let the tape actually touch the header at any point - just wrap it around the shirt or towels themselves. This will help protect the finish when you fit the header through the opening underneath the car.
3. The included instructions call for the header to be installed in two pieces, but I believe it can fit as a single piece. I didn't try it that way, but after installing another (1-piece) header, I found it much easier to handle it as a single piece. Be sure to insert the included gaskets when joining the upper and lower portion with the included bolts. (If you successfully install a DC Sports header as a single piece, let us know and I will update the article.)
4. Once the header is lined up properly with the head (make sure the manifold gasket on the head side is properly aligned), torque the nuts and bolts to 33 lb-ft (some may be easier to reach from above). If you are installing the header in two pieces, the job is much easier if you have a helper holding the upper portion in place from above.
5. On the catalyst side, torque the nuts to 25lb-ft. Don't forget to insert the 3rd (included) hard O-ring gasket between the cat and the rear flange on the header.
6. Install the 02 sensor into the bung on the DC Header and torque it to 33lb-ft.
7. Remove the protective padding from the header and then clean the header as well as you can. Double check all of the connections.
8. Lower the car off the jack stands
9. Start the motor and listen for any signs of exhaust leaks. If all sounds well, take it for a spin and enjoy. If there is definitely a leak, don't drive the car until it is identified and fixed.

Overall, I found the installation to be very straightforward with (thankfully) no "gotchas". All told, I managed to get it done in less than 90 minutes, and that included lots of interruptions for photography. It could be done in well under an hour, particularly if you have access to a lift. There are no major clearance issues and the DC Sports header fits in place easily.

Driving Impressions