Why Upgrade to Borla Headers on Your Subaru BRZ?

The Subaru BRZ (and its Toyota 86/Scion FR-S siblings) is a driver’s car from the factory, but its naturally aspirated FA20 engine comes with restrictive exhaust manifolds designed primarily for emissions and noise compliance. Swapping in a set of aftermarket headers, especially the high-quality Borla headers, is one of the most effective bolt-on modifications for unlocking real horsepower and torque gains. Borla’s engineering focuses on equal-length primary tubes that improve exhaust scavenging, reduce back pressure, and produce a more aggressive exhaust note without excessive drone. With a proper installation, you can expect gains of 10–15 wheel horsepower and a noticeable improvement in throttle response across the mid-range and top end. This guide provides a detailed, step-by-step approach to installing Borla BRZ headers safely and effectively, ensuring your vehicle achieves maximum performance and reliability.

Tools and Materials You Will Need

Having the correct tools on hand before you begin will prevent frustration and speed up the job. While the process is straightforward, certain fasteners are notoriously tight on the FA20 engine, so quality tools are essential.

Essential Hand Tools

  • Socket set: A ⅜” drive metric socket set (10mm, 12mm, 14mm, 17mm, 19mm) – note that header bolts typically require a 12mm or 14mm socket, while exhaust flanges use 14mm. A 10mm socket is for heat shield bolts. An 8mm socket may be needed for small bracket bolts.
  • Torque wrench: A ⅜” or ½” drive torque wrench capable of reading 15–40 lb-ft. The header-to-head bolts are critical and must be torqued precisely.
  • Ratchet and extensions: A 3” and 6” extension and a universal joint (swivel socket) will help reach awkward bolts under the intake manifold.
  • Wrenches: Combination wrenches in 12mm, 14mm, 17mm – especially for the header stud nuts and O2 sensor removal.
  • O2 sensor socket: A 7/8” (22mm) O2 sensor socket or a crows-foot wrench for the wideband O2 sensor located on the header collector. A flare nut wrench (12mm) for the upstream sensor if you reuse the factory sensor.
  • Pry bar or panel remover: To release stubborn clips and rubber hangers.
  • Jack and jack stands: A low-profile floor jack and two strong jack stands (rated for at least 2 tons). Ramps can work with caution, but stands are safer for under-car work.
  • Penetrating oil: A product like WD-40 Specialist Penetrant or Liquid Wrench – spray all exhaust nuts and bolts the night before to reduce corrosion.

Consumables and Replacement Parts

  • New gaskets: Borla headers usually come with gaskets, but having a fresh set of OEM or aftermarket exhaust manifold gaskets (part number 14045AA130 for the cylinder head, and a gasket for the front pipe connection) ensures a leak-free seal. Never reuse old gaskets.
  • Anti-seize compound: Copper or nickel-based anti-seize is crucial for header studs and O2 sensor threads to prevent galling and future removal issues.
  • High-temperature thread locker: Optional but recommended for the header bolts – use medium strength (blue) if you plan to remove headers again; high strength (red) only if you never want them loose.
  • New exhaust hardware: Replace the spring bolts and nuts for the front pipe connection; these often corrode. A galvanized or stainless steel spring bolt kit is cheap insurance.
  • O2 sensor bung plug or extender: Some aftermarket headers move the downstream O2 sensor location; you may need a spark plug anti-fouler to prevent a check engine light (CEL) from the secondary O2 sensor.
  • Shop towels and brake cleaner: To clean the mating surfaces and remove old gasket material.

Preparation and Safety Precautions

Before you crawl under the car, take these critical preparation steps to ensure a smooth installation and protect both you and your BRZ.

Vehicle Positioning and Electrical Safety

  • Disconnect the negative battery terminal: Use a 10mm wrench to remove the negative cable and safely isolate it from the battery post. This prevents electrical shorts and resets the ECU for the new headers (though the ECU will need a few drive cycles to relearn).
  • Park on level ground: Engage the parking brake and chock the rear wheels.
  • Raise the vehicle: Locate the factory jack points on the side rocker panels (the reinforced pinch weld areas). Place the floor jack under the front cross member or driver/passenger side jack points. Lift the car high enough to work comfortably (approx. 18–20 inches of clearance). Place jack stands under the front subframe or designated lift points – never rely on the jack alone.
  • Remove underbody covers: The BRZ has a plastic engine under tray. Use a 10mm socket or Phillips screwdriver to remove the clips and screws. Lower the tray and set it aside.

Additional Preparation Tips

  • Spray penetrating oil: The previous evening, liberally spray all exhaust manifold flange nuts, O2 sensors, and the front pipe connections. Let the oil soak overnight to break down rust.
  • Let the exhaust cool completely: If the car has been driven, wait at least 2 hours before working on the exhaust. Hot components can cause severe burns, and thermal expansion makes bolts tighter.
  • Wear protective gear: Safety goggles, work gloves, and a long-sleeved shirt are non-negotiable. Exhaust systems accumulate carbon and fine metal particles.

Removing the Factory Exhaust Manifold (Headers)

The stock headers are a single-piece cast iron manifold that is heavy and restrictive. Removing them requires working in tight spaces near the oil filter and steering rack. Take your time – patience prevents stripped fasteners and broken bolts.

Step 1: Disconnect the Front Pipe

  • Locate the connection between the stock header collector and the front pipe (also called the over-pipe on some BRZs). It is directly below the engine, near the oil pan.
  • Use a 14mm socket to remove the two spring bolts. You may need a pry bar to separate the flanges if they are rusted together. Do not force the pipe; gentle persuasion with a soft mallet helps.
  • Disconnect the O2 sensor wiring harness from the engine bay bracket. The upstream O2 sensor (before the cat) is located on the header collector. Use an O2 sensor socket or 22mm wrench to unscrew it. Note: this sensor is delicate – do not drop it or damage the ceramic element. If it is stuck, apply more penetrating oil and use a breaker bar with a socket. If the sensor refuses to move, heat the bung with a torch (if available) to expand the metal.

Step 2: Remove Heat Shields

  • The factory heat shield is held by two 10mm bolts on top of the manifold, and one or two 10mm bolts from the bottom. Access the top bolts from above after removing the intake pipe (a 2-minute task – unclamp the MAF sensor harness and loosen the clamps on the throttle body and airbox). The bottom bolts are easier from underneath.
  • Place the heat shield aside; it will not be reused with Borla headers as the aftermarket headers have their own design or you may choose to run without a shield (ensure sufficient clearance from brake lines and wiring).

Step 3: Unbolt the Header from the Cylinder Head

  • Working from underneath the car, locate the 8–10 studs or bolts that secure the manifold to the cylinder head. The FA20 engine has a symmetrical layout: six studs on each side (left and right banks) plus a few bracket bolts. Typically, you will remove twelve 12mm or 14mm nuts (or bolts) – check your specific model.
  • Use a 12mm socket with an extension and a universal joint for the rear bolts that are blocked by the intake manifold runner. A ratcheting wrench can also be helpful.
  • Spray more penetrating oil on the studs and let it sit for 10 minutes before attempting to loosen. Turn each fastener a quarter turn at a time to reduce binding.
  • Once all fasteners are loose, carefully slide the stock header out from the engine bay, tilting it to clear the subframe. On BRZs, you may need to disconnect the engine mount bolt (17mm) and use a jack to lift the engine slightly for clearance – but with proper maneuvering, the stock header can be removed without lifting the engine. If you encounter resistance, try removing the oil filter (protect the area with a rag) for extra space.

Step 4: Clean the Mating Surfaces

  • Use a plastic scraper or a razor blade with extreme caution to remove all old gasket material from the cylinder head flanges. Do not scratch the aluminum head surface. Wipe the area with brake cleaner and a lint-free cloth.
  • Inspect the header studs for corrosion or damage. If a stud is damaged, replace it now. Otherwise, clean the threads with a wire brush and apply anti-seize.

Installing the Borla Headers

Borla headers for the BRZ are typically constructed from 304 stainless steel with mandrel-bent tubes, TIG-welded collectors, and a high-flow catalytic converter (if you purchased the catted version) or a performance catless design. The installation process is the reverse of removal, but attention to detail ensures a leak-free seal and long-lasting performance.

Step 1: Apply Anti-Seize and Install New Gaskets

  • Place the new gaskets onto the cylinder head studs with the raised metal ring facing the header flange. The gasket should fit snugly – tap it with a rubber mallet if needed.
  • Apply a thin coat of anti-seize compound to all stud threads and to the back side of the nuts. Do not over-apply; anti-seize can migrate and contaminate O2 sensors if it gets inside the exhaust.

Step 2: Position the Borla Headers

  • From underneath the car, lift the header assembly into position. The equal-length tubes will angle toward the front of the engine. Align the two collector flanges with the front pipe connection. Ensure the O2 sensor bungs are oriented so the sensors can be re-installed without interference with the steering shaft or subframe. Some aftermarket headers require the downstream O2 sensor to be relocated – use the included extender cable or anti-fouler.
  • Hand-thread the header-to-head nuts onto the studs. Start at the center pair and work outward. This ensures even seating and prevents header flange warping.
  • Once all nuts are snug by hand, use a torque wrench to tighten them in a cross pattern to the factory specification 15–18 lb-ft (20–24 Nm). Do not exceed this torque; the aluminum threads in the head can strip. Check the Borla instructions – some recommend 14–16 lb-ft.

Step 3: Connect the Front Pipe

  • Install a new gasket between the header collector and the front pipe. Use the supplied or new spring bolts and washers. The springs allow for thermal expansion and reduce vibration.
  • Tighten the spring bolts so the spring compresses about halfway; exact torque is not critical – typically 20–25 lb-ft for the nuts. Ensure the flanges are parallel and not binding.

Step 4: Reinstall O2 Sensors

  • Apply anti-seize to the threads of both O2 sensors (avoid getting any on the sensor tip). Screw the upstream sensor into the bung on the header collector. Use an O2 sensor socket to tighten it to 25–30 lb-ft (do not over-tighten).
  • For the downstream sensor (post-cat), install it in the bung provided on the new header. If a CEL is likely due to the removed catalytic converter, you may need a mechanical anti-fouler or a tune to suppress the code.
  • Secure the sensor wires to the factory brackets with zip ties to prevent contact with the hot exhaust.

Step 5: Reattach Heat Shielding (Optional)

  • Borla headers often run hotter than stock, so it is wise to reinstall the heat shield if possible. However, the factory shield may not fit over the equal-length tubes. Aftermarket heat wrap or a custom shield can be fabricated. If you skip the shield, double-check that wires, brake lines, and steering components have at least ½” clearance.

Step 6: Final Checks Under the Hood

  • Reinstall the intake pipe and MAF sensor.
  • Check all nuts and bolts once more – especially the header-to-head nuts – after a heat cycle. Thermal expansion may cause slight loosening. Re-torque them after the first test drive (when cool).
  • Reconnect the negative battery terminal.

Post-Installation Procedures and Tuning Considerations

After the hardware is installed, the job is not quite complete. The engine management system must adapt to the changes in exhaust flow.

Checking for Exhaust Leaks

  • Start the engine with the car up on jack stands. Listen for a ticking or hissing sound at the header connections. If you suspect a leak, use a soapy water spray bottle on the flanges; bubbles indicate an air leak.
  • Let the engine reach operating temperature. The exhaust manifold will glow faintly at idle – this is normal for thin-wall stainless steel headers. If a persistent leak is found, tighten the bolts slightly (engine off, cool) or replace the gasket.

ECU Adaptation and Tuning

  • The stock ECU will initially run a bit lean after header installation because the O2 sensors now read a different flow pattern. Do not panic – the long-term fuel trims will adjust over 50–100 miles of mixed driving.
  • However, for maximum power and to avoid a check engine light (especially on catless headers), a professional tune (ekanoo, ECUTEK, or COBB Accessport) is highly recommended. A tune can also take advantage of the increased flow for gains of 15–20 hp.
  • If you do not tune, you may encounter a P0420 catalyst efficiency code. Using a spacer (anti-fouler) on the downstream O2 sensor can often clear the code, but it is a band-aid. A tune is a better long-term solution.

Test Drive

  • Lower the car and ensure the parking brake is off. Take a slow test drive around the neighborhood, then progressively open the throttle. Listen for any rattling – the header tubes may contact the steering shaft or subframe if not properly positioned. If you hear a metallic knock, stop immediately and check clearance; a gentle pry or tap with a mallet on the header tubing can resolve minor clearance issues.
  • After the drive, park and let the engine cool completely. Re-torque the header nuts to spec and re-check all O2 sensor connections.

Performance Gains and Expected Results

With correctly installed Borla headers, you can expect the following:

  • Peak horsepower increase: 8–12% gain at the wheels (approximately 8–15 hp depending on the specific model and supporting mods). The torque curve shifts upward, with noticeable pull from 4000–7000 RPM.
  • Improved exhaust sound: The Borla headers produce a deeper, more aggressive tone that maintains a mature character – no excessive rasp or drone when paired with a quality cat-back exhaust.
  • Weight reduction: The factory cast iron manifold weighs around 15 lbs, while the Borla stainless steel unit weighs roughly 5–6 lbs. This reduces vehicle weight and improves mass centralization.

Common Mistakes to Avoid

  • Over-tightening header bolts: The FA20 cylinder head threads are aluminum and easily stripped – always use a torque wrench and never exceed 18 lb-ft.
  • Reusing old gaskets: Always install new gaskets; old ones will leak.
  • Skipping the anti-seize: Header bolts and O2 sensors will seize after exposure to high heat, making future removal difficult.
  • Ignoring O2 sensor location: The downstream sensor must be placed correctly to avoid a CEL. Check your local laws regarding cat removal – some areas require a catalytic converter to pass emissions.
  • Forgetting to reset the ECU: Disconnecting the battery resets fuel trims; if you skip this, the ECU may take longer to adapt.

Conclusion

Installing Borla headers on your Subaru BRZ is a satisfying DIY project that yields tangible performance and sound improvements. By following this comprehensive guide and using the proper tools and techniques, you can complete the installation in a weekend. The key to success is patience during disassembly, cleanliness during reassembly, and attention to torque specifications. Remember that an aftermarket tune unlocks the full potential of the headers, so budget accordingly. If you encounter stubborn bolts or aren’t comfortable with engine bay work, don’t hesitate to consult a professional shop.

With the new headers in place, your BRZ will feel sharper, sound better, and deliver the driving engagement that makes this platform so beloved.

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