How to Install the HKS Header W/ Cat on a Subaru BRZ

Initially, before starting on any project on the front of the car, you would want to get it in the air. Supported by Jack stands.

There are various bolts on the back under tray that need to be taken off with a 10mm socket

There are 11 Bolts that have to be taken off to remove the black under tray.

After getting the rear under tray off, its time to move on to the front under tray.

Theres 7 black clips that require a flat head to pop out. Be careful not to break the head on these. Once they pop out, just pull them out of the hole.

After the Clips are out, go ahead and use the 10mm socket to get the bolts out. There should be (8) 10 mm head bolts holding up the under tray.

Once those bolts are taken out, the under tray will drop. Be careful not to damage the tray as it is a key item in the undercarriage of the vehicle.

First step is to unbolt the nuts from the front pipe that connects to the cat back part of the exhaust. Keep these, as they will be reused later on.

Caution, depending on your region's weather condition, oxidation must make it difficult to remove nuts.

Using a 14mm wrench, remove the two nuts holding the frontpipe to the overpipe.

Utilizing a 14mm wrench, remove the bolt supporting the front pipe to the transmission mounting bracket.

With the front pipe being supported by the hook on the center bracket, separate the front pipe from the catback.

Remove front pipe from center bracket. Some pressure on the bracket may be required.

Front pipe can now be separated from the overpipe studs.

Now that you have the Stock front pipe out, you are now ready for the install of the replacement front pipe, or any other exhaust component.

After the removal of the front pipe, you are now ready to move on to the over pipe.

Remove the nuts securing the overpipe to the header. A 14mm gear wrench is suggested.

Remove the four 10mm bolts and one 10mm nut securing the heat shield to the overpipe. Remove the heat shields.

With the heat shields removed, you may now maneuver the overpipe forward and under the header.

After removing the under trays and the 2 exhaust components, you are now ready to tackle the header. Be sure to confirm that you are able to remove the o2 Sensors because you shouldnt continue without removing them.

You now have to un-clip the two o2 sensor pig tails. The black and the grey one.

You also need to disconnect the clip securing the o2 sensor wires to the front of the motor.

You may now remove the o2 sensor. Be careful not to strip or round the head of the sensor, as it will make it more difficult to remove.

For the next o2 sensor removal, we recommend an o2 sensor removal tool.

With the o2 sensor removal tool, go ahead and remove the o2 sensor on top portion of the header.

While supporting the header, loosen the 3 nuts holding the left side of the header to the head. (Loosen the nuts slowly on the left side of the header). Make sure to support he left side of the header. Do not allow it to sag.

You may now lower the header carefully to remove it.

After the removal of the front pipe, over pipe and the stock header, the HKS Catted Header is now ready for install.

Before installing the header, make sure that all the exhaust manifold studs are clean and free of debris.

Its good to clean up the threads and the mating area. You can scuff the areas with a light scuffing pad to make sure the gaskets make a definitely seal for a leak proof install.

Now the tricky part with the header install is holding the gaskets in place while you lift the header to line up with the studs.

With your partner, hold the gasket to the flange of the header while lifting it up to mate with the engine. Once lined up and the studs are through the gasket and flange, you're ready to thread on the nuts.

With header slipped through the studs and the gasket sandwiched between, go ahead and start threading the nuts on. These nuts can support the weight of the header so you can let go once the nuts are on the studs.

Once the header bolts are all torqued to spec, you can now install the over pipe to the header. (see over pipe install if you forgot how to do it)

Make sure to use locktite on the bolts.

Don't forget to adjust the o2 sensor pigtail holder.

Then install the o2 sensors and extensions if needed.

Then button the car up and make sure the bolts are all tightened.

With a lighter and better flowing header, an increase in power and throttle response will definitely be noticed.

Go ahead and button everything else up and enjoy your new found horsepower!