Installing aftermarket headers on your Subaru BRX (or Toyota 86/Scion FR-S) is one of the most effective bolt-on modifications for unlocking significant horsepower and torque gains. The factory exhaust manifolds are notoriously restrictive, with integrated catalytic converters that choke airflow and create heat buildup. By replacing them with a set of performance headers—such as the oft-recommended equal-length or unequal-length designs from brands like Injen, Borla, Tomei, or Gruppe-S—you can expect a noticeable improvement in throttle response, a lighter exhaust note, and gains of 10–20 horsepower at the wheels with proper tuning.

This guide walks you through the entire installation process from start to finish, covering the necessary tools, safety precautions, step-by-step removal, installation, and post-installation checks. We’ll also discuss common pitfalls, torque specifications, and why an ECU tune is recommended to fully exploit your new headers. Whether you’re a seasoned DIYer or a motivated beginner, follow along to complete the job safely and efficiently.

Understanding the Benefits of BRZ Headers

Headers replace the factory exhaust manifold with smoother, larger-diameter tubes that merge into a collector. The primary benefit is reduced backpressure and better scavenging of exhaust gases, which allows the engine to expel spent gases more efficiently and draw in a fresh air-fuel charge. This translates into midrange torque gains and a higher peak horsepower ceiling.

Depending on the design, you may choose between:

  • Unequal-length headers – retain the classic Subaru “boxer rumble” sound but may have slightly less high-rpm power.
  • Equal-length headers – produce a smoother, more refined tone and often offer better top-end power, common on fa20 engines with proper tuning.

Regardless of your choice, installing headers also reduces under-hood temperatures, as the stock cast-iron manifold soaks and radiates heat. Many aftermarket headers are made from lightweight stainless steel or mild steel, often with ceramic coating to further manage heat.

Tools and Parts Required

Having the right tools on hand before you start saves time and frustration. Here’s a comprehensive list:

  • New BRZ headers (include gaskets if provided, otherwise purchase separate
  • Socket wrench set – metric (10mm, 12mm, 14mm, 17mm) and extensions, swivel sockets for tight spaces
  • Torque wrench – capable of reading in ft-lb and in-lb ranges
  • Gasket scraper or razor blade
  • New exhaust gaskets – for header-to-engine block (copper or multi-layer steel recommended) and header-to-midpipe (donut gasket)
  • Penetrating oil (PB Blaster or WD-40 Specialist) – for rusted bolts
  • Jack and jack stands (or a lift)
  • Safety glasses and mechanic gloves
  • Rags and a drain pan (if any fluid spills)
  • Torch (optional, for stubborn bolts)
  • Anti-seize compound for threads
  • O2 sensor socket (if reusing or swapping O2 sensors)

Pro tip: Consider replacing the O2 sensors while you have the headers off, especially if they’re original with high mileage. A faulty sensor can cause poor drivability and check-engine lights.

Safety Precautions

Working under a vehicle with exhaust components involves heat, heavy parts, and sharp edges. Always follow these safety practices:

  • Work on a level surface and use jack stands rated for the vehicle’s weight. Never rely solely on a hydraulic jack.
  • Allow the engine and exhaust system to cool completely before starting. The catalytic converters stay hot long after shutdown.
  • Wear safety glasses to protect against debris and rust flakes.
  • Use gloves when handling gaskets and metallic components (sharp edges, anti-seize chemicals).
  • Disconnect the battery negative terminal to prevent short circuits and accidental airbag deployment.
  • If you use a torch to heat bolts, keep a fire extinguisher nearby and avoid setting flammable materials on fire.

Preparation Steps

Proper preparation ensures a smoother process and reduces the chance of mistakes.

  1. Park and secure the vehicle. Engage the parking brake and place wheel chocks behind the rear wheels.
  2. Disconnect the battery negative terminal. Use a 10mm wrench to loosen the terminal, then tuck the cable away from the post.
  3. Raise the vehicle. Use a jack to lift the front of the car high enough to slide jack stands under the front subframe. Lower the car onto the stands securely.
  4. Access the underside. Once stable, verify the vehicle won’t tip. Clear away any loose underbody panels (there are often plastic covers held by 10mm bolts or clips near the oil pan area).
  5. Spray penetrating oil. Apply penetrating oil to all exhaust bolts (header bolts, O2 sensor threads, midpipe flange bolts) 30 minutes prior to removal. This will save you a lot of swearing.

Step 1 – Removing the Stock Headers

The factory header assembly includes two separate pieces for the FA20 engine: the left and right manifolds, each with a catalytic converter. Here’s how to remove them:

  1. Locate the header bolts. On the FA20, there are six nuts (12mm) per manifold securing it to the engine block (two studs per cylinder head, three per side). You may also need to unbolt the heat shields.
  2. Remove the O2 sensors. Unplug the electrical connectors (they’re clipped onto brackets near the intake manifold). Use an O2 sensor socket to unscrew the sensors from the headers. Be careful not to damage the wiring or threads.
  3. Unbolt the header-to-midpipe connection. There’s a flange just after the collector with two 14mm nuts/bolts. If the gasket is stuck, gently pry it apart.
  4. Remove the manifold support bracket. The factory headers are supported by a bracket bolted to the engine block. Use a 12mm socket to remove it.
  5. Lift out the headers. With all bolts removed, rock the manifolds free from the studs. They may be stubborn; use a pry bar gently between the flange and block. Lower them from the engine bay or from underneath. You’ll likely need to disconnect that support bracket first.
  6. Remove the old gaskets from the cylinder head exhaust ports. Use the gasket scraper to clean off any remaining material. Be careful not to scratch the head surface.

Step 2 – Preparing the Engine Block Surface

After the old headers are off, you’ll see the exhaust ports on the cylinder heads. Thoroughly clean them:

  • Scrape away any carbon buildup or old gasket material with a brass scraper or razor blade (use a light touch to avoid gouging the aluminum heads).
  • Wipe the surface with a clean rag and brake cleaner to remove oil and debris.
  • Check the studs: If any are damaged or wobbly, replace them now. Threaded studs are common on the FA20; if one breaks, you’ll need an extractor kit.
  • Apply a thin film of anti-seize to the stud threads (copper or nickel-based works best with exhaust heat) to ease future removal.

Step 3 – Installing the New BRZ Headers

Now that the engine surface is clean, you can fit the new headers. Follow this sequence carefully.

  1. Place new gaskets on the studs. Use the gaskets that came with your headers, or aftermarket copper gaskets for better crush and sealing. Make sure they are oriented correctly (most are marked “EX” or “exhaust side”).
  2. Position the new header sets (left and right) over the studs. Depending on the design, you may need to install the header in two pieces (some designs have separate collector pieces). Engage the studs loosely by hand.
  3. Hand-tighten the header nuts onto the studs in a crisscross pattern to draw the header evenly against the gasket. Do not yet torque to spec.
  4. Reinstall the O2 sensors. Thread them into the new header bungs. Use new crush washers or anti-seize on the threads (be careful not to get anti-seize on the sensor tip). Torque to 30-33 ft-lb.
  5. Tighten the header nuts to factory torque specs. For the FA20, the recommended torque for header-to-head nuts is 18 ft-lb for the M8 nuts. Use a torque wrench in the same crisscross pattern. Do not overtighten; you can strip the studs or distort the flange.
  6. Install the header support bracket (if using a single-piece header design) or the bracket that often connects the collector to the engine block. Torque to 18 ft-lb.

Note: If you’re installing equal-length headers, you may also need to install an aftermarket oil pickup tube or clear alternator clearance issues—check your specific brand’s instructions.

Step 4 – Reconnecting the Exhaust System

With the headers bolted to the engine, you now need to connect the rest of the exhaust.

  1. Fit a new donut gasket (or flat gasket depending on design) between the header collector flange and the front pipe (over-pipe). Apply anti-seize to the studs if they’re prone to rust.
  2. Join the header to the front pipe/overpipe. Line up the flanges and insert the bolts. Hand-tighten, then torque to 30-35 ft-lb. Use a cross pattern if there are multiple bolts.
  3. Reattach any support brackets from the header to the transmission or engine block—these reduce vibration and stress on the welds.
  4. If your cat-back exhaust was removed, reconnect it at the midpipe connection. Torque those flanges similarly.
  5. Inspect all joints for alignment. You may need to loosen rear hangers and adjust the exhaust to prevent rattling against the subframe or heat shields.

Final Steps and Post-Installation Checks

Once everything is bolted up, perform these checks before lowering the car:

  1. Reconnect the battery negative terminal.
  2. Lower the vehicle to the ground. Do not start the engine yet.
  3. Double-check all fasteners – header nuts, O2 sensors, flange bolts, and support brackets. Make sure they’re all at the correct torque.
  4. Start the engine and let it idle. Listen for ticking or hissing sounds that indicate an exhaust leak. A small leak near the head can be audible and may smell of exhaust.
  5. Feel around the header flanges (carefully, they’ll be hot quickly) – use a gloved hand or a piece of paper near the joints to detect air leaks. A better method: use a smoke machine or spray soapy water on the joints (be careful of hot surfaces). If you see bubbles, tighten the bolts slightly.
  6. Test drive. Take a short drive to allow the system to heat-cycle. After cooling, re-torque the header nuts and flange bolts. Thermal expansion often loosens them slightly.
  7. Check for error codes. If you removed O2 sensors or relocated them, you may trigger a check-engine light for catalyst efficiency. This is normal if you don’t have a tune. Plan to have the car tuned soon.

Common Mistakes to Avoid

  • Over-tightening header nuts. The studs are small (M8) and can snap. Always use a torque wrench and respect factory specs.
  • Reusing old gaskets. Exhaust gaskets are one-time-use for optimal sealing. New gaskets cost little and prevent leaks.
  • Not replacing O2 sensor gaskets. The crush washer on the O2 sensor should be replaced if removed. A small leak here can cause false readings.
  • Forgetting anti-seize. Stainless steel bolts and aluminum heads are prone to galling. Apply anti-seize to all threads in contact with aluminum and exhaust bolts.
  • Ignoring clearance issues. Some headers push the midpipe or alternator. Check for clearance before final tightening. Use spacers or adjust hangers as needed.

Performance Gains and ECU Tuning

Headers alone will give the engine a richer sound and slight low-end response, but the real gains come with an engine tune. The stock ECU is calibrated for the restrictive factory headers; after installation, the air-fuel ratios will likely be richer in some areas and leaner in others. Without tuning, you may experience:

  • Random check-engine lights (e.g., P0420 catalyst efficiency).
  • Rough idle or hesitation due to changed exhaust scavenging.
  • Suboptimal power gains (the headers may actually reduce power if the ECU cannot adapt fully).

We strongly recommend custom tuning or a flash tune from a reputable source like Delicious Tuning, ECUTek, or a local dyno tuner. Many off-the-shelf maps exist for the BRZ with headers and a full exhaust. A proper tune can yield an additional 8–15 horsepower and smooth out the power curve.

If your area requires emissions compliance, note that removing the primary catalytic converter (which is integrated into the stock headers) will cause the vehicle to fail a visual inspection. Some aftermarket headers come with a high-flow catalytic converter option – consider those if you need to pass smog. Others install a secondary O2 spacer or mini-cat to avoid codes.

Conclusion

Installing a set of performance headers on your Subaru BRZ is a rewarding project that sharpens throttle response, increases power, and gives your car a more aggressive exhaust note. With the right tools, patience, and attention to detail, you can complete the job in a weekend. Always prioritize safety by using jack stands, wearing protective gear, and keeping a fire extinguisher nearby.

Once installed, take the time to check for leaks and re-torque after heat cycling. And remember: to truly unlock the potential of your new headers, invest in an ECU tune. Pairing headers with a good tune will give you the best bang for your buck, transforming your BRZ into a noticeably faster and more responsive machine.

If you encounter any issues during installation, consult model-specific forums like FT86 Club or NASIOC for advice. And if you are not comfortable working with exhaust systems or engine sensors, do not hesitate to enlist a professional mechanic.