Why Upgrade to Cosworth S2000 Headers

The Cosworth S2000 headers represent a significant performance upgrade for the Honda F20C and F22C engines. Designed with equal-length primary tubes and a carefully merged collector, these headers improve exhaust gas scavenging, which reduces backpressure and helps the engine breathe more freely at high rpm. The result is a measurable gain in peak horsepower and torque, typically in the 10–15 hp range on an otherwise stock engine, with even larger gains when combined with a fresh tune or supporting modifications such as a high-flow catalytic converter and cat-back exhaust system. Beyond the performance benefits, the Cosworth headers deliver a more aggressive, refined exhaust note that highlights the S2000's signature high-rpm howl without introducing excessive drone or harshness at cruising speeds. The headers are constructed from 304 stainless steel and feature precision CNC-machined flanges, ensuring a durable, corrosion-resistant fit that outlasts OEM components under hard use. For enthusiasts who track their cars or simply want a more engaging street driving experience, the Cosworth S2000 headers offer an excellent balance of power, sound, and build quality.

Tools, Materials, and Safety Equipment

A successful header installation depends on having the right tools on hand before you begin. The following list covers everything you will need to complete the job efficiently and safely.

Hand Tools and Shop Equipment

  • Socket set (metric, 3/8-inch and 1/2-inch drive): You will need a range of sockets from 10 mm to 19 mm, with 12 mm, 14 mm, and 17 mm being the most common sizes for exhaust manifold bolts and support brackets.
  • Torque wrench (1/2-inch drive, 20–150 ft-lb range): A reliable torque wrench is essential for tightening header bolts and flange nuts to the factory-recommended specifications. Overtightening can warp flanges or strip threads.
  • Ratchet and extension bars (3-inch, 6-inch, and 12-inch extensions): The S2000's engine bay is tight, and extensions help reach bolts that are tucked behind the block or near the firewall.
  • Swivel or universal joint sockets: These are helpful for accessing bolts at awkward angles, particularly on the lower studs of the exhaust manifold.
  • Breaker bar (18-inch or longer): Exhaust manifold bolts on a car that has accumulated heat cycles can be stubborn. A breaker bar gives you the leverage needed to break them loose without damaging the fastener.
  • Jack and two jack stands (minimum 2-ton capacity): You will need to raise the front of the vehicle to access the underside of the exhaust system. Always use jack stands, not just the jack, to support the vehicle while you work underneath it.
  • Trim removal tools or flathead screwdriver: These are used to remove plastic clips and fasteners from the undertray and any trim pieces blocking access.
  • Penetrating oil (such as PB Blaster or WD-40 Specialist): Spraying the exhaust manifold studs and bolts the night before can save hours of frustration during removal.

Parts and Consumables

  • Cosworth S2000 headers (part number varies by model year): Ensure you order the correct version for your vehicle. AP1 (2000–2003) and AP2 (2004–2009) engines have subtle differences in port shape and flange orientation.
  • New exhaust manifold gaskets: Cosworth headers typically require the same multi-layer steel (MLS) gasket used by the OEM. Always replace the gasket when swapping headers; reusing the old gasket risks exhaust leaks at the head flange.
  • New exhaust gasket for the collector-to-catalytic-converter joint: This is a separate donut or flat gasket depending on your year and aftermarket exhaust configuration. Verify the gasket style before starting the job.
  • Header bolts or studs (if not included with the headers): Cosworth headers often come with new hardware, but double-check the package contents. If you need to purchase separately, use Grade 8 or equivalent high-strength fasteners.
  • Anti-seize compound (copper or nickel-based): Applying a small amount to the threads of the header bolts prevents galling and makes future removal easier.
  • High-temperature RTV silicone (if required for the collector joint): Some exhaust connections benefit from a thin bead of RTV to ensure a leak-free seal. Use a product rated for continuous exhaust temperatures.

Safety Gear

  • Safety glasses or goggles: Falling debris, rust particles, and penetrating oil splashes are common during exhaust work. Protect your eyes from the moment you begin until the job is finished.
  • Mechanic gloves (cut-resistant or nitrile-coated): Exhaust components are sharp and covered in carbon and rust. Gloves protect your hands and improve grip on oily fasteners.
  • Long sleeves and pants: Hot coolant, oil drips, and sharp metal edges make close-fitting work in the engine bay hazardous. Dress appropriately for the task.

Preparing the Vehicle and Workspace

Proper preparation minimizes the risk of mistakes and ensures that the installation proceeds smoothly. Follow these steps before touching any exhaust hardware.

Park, Secure, and Isolate

  1. Park on a level, solid surface and engage the parking brake firmly. Chock the rear wheels to prevent any unintended movement.
  2. Disconnect the negative battery terminal from the battery. This step prevents accidental short circuits when working near the alternator, starter, or wiring harnesses. It also resets the ECU's learned fuel trims, which can help the engine adapt more quickly to the new exhaust flow after reassembly.
  3. Raise the front of the vehicle using a floor jack placed on the front crossmember or subframe. Once raised, lower the vehicle onto jack stands positioned under the factory jacking points or subframe connectors. Double-check that the vehicle is stable before crawling underneath.
  4. Remove the plastic undertray if it is still in place. The undertray is held by a combination of 10 mm bolts and plastic push-pin clips. Set the undertray aside in a safe location so it does not get damaged.

Access and Clearance

With the vehicle raised and the undertray removed, inspect the area around the exhaust manifold. On the S2000, the manifold sits close to the engine block and is partially obscured by the intake manifold on the passenger side. Depending on your specific model year and whether you have an aftermarket intake system, you may need to remove the intake manifold or the air intake ducting to access the upper header bolts. If you have an aftermarket cold-air intake, unbolt the intake tube and move it aside. If the intake manifold must come off, label the vacuum lines and electrical connectors before disconnecting them to simplify reassembly.

Removing the Factory Exhaust Manifold

Removing the stock manifold requires patience, especially if the car has accumulated significant mileage. The bolts are exposed to repeated heating and cooling cycles, which can cause them to seize or gall. Taking a careful approach prevents broken studs and damaged threads.

Disconnect Sensors and Brackets

  1. Locate the primary oxygen sensor (O2 sensor) that is threaded into the factory manifold. On the S2000, this sensor is usually located on the rearward runner of the manifold, near the firewall. Unplug the sensor connector from the wiring harness, then use a 22 mm O2 sensor socket to unscrew the sensor from the manifold. Set the sensor aside in a clean location where the tip will not be contaminated by grease or dirt. Be gentle; O2 sensors are sensitive to impact and contamination.
  2. Remove any support brackets that connect the manifold to the engine block or transmission housing. The factory manifold often has a support bracket near the collector that must be unbolted to free the manifold fully.
  3. If your vehicle has a heat shield covering the manifold, remove it by unbolting the small nuts or bolts that hold it in place. The heat shield can be discarded if you are installing aftermarket headers, as the Cosworth headers have their own thermal management characteristics and the shield will no longer fit properly.

Unbolt the Manifold from the Cylinder Head

  1. Apply penetrating oil to each of the manifold-to-head studs and bolts. Allow the oil to soak in for at least 10 minutes before applying torque. If the bolts are severely rusted, repeat the application.
  2. Using a socket and breaker bar, loosen the manifold nuts in a reverse crisscross pattern. Start with the outermost nuts and work inward. This pattern reduces the risk of warping the manifold flange as you release the tension.
  3. Once all nuts are loose, remove them by hand and set them aside in a labeled container. You will not reuse these nuts; they should be replaced with new hardware to ensure proper clamping force and thread integrity.
  4. Carefully wiggle the manifold free from the studs. It may be stuck due to carbon buildup or corrosion. Gently tap the manifold flanges with a rubber mallet if needed, but avoid hitting any sensor bungs or thin-walled tubing. Do not pry against the cylinder head surface with a metal tool, as this can damage the mating surface and cause a vacuum leak.
  5. Lower the manifold out of the engine bay from underneath the vehicle. On the S2000, the manifold usually comes out more easily from below, especially if you have removed the undertray and have adequate clearance.

Inspect and Clean the Mating Surface

With the factory manifold removed, inspect the cylinder head's exhaust port mating surface. Look for any remnants of the old gasket, carbon deposits, or scoring. Use a plastic scraper or a non-abrasive pad to carefully clean the surface. Do not use sandpaper or a metal scraper, as you can gouge the aluminum head and create a leak path. Wipe the surface with a clean rag and brake cleaner to remove any oil or debris. Also inspect the studs that remain in the cylinder head. If any studs are loose, stripped, or damaged, now is the time to replace them. A helicoil or timesert may be necessary if the threads are compromised.

Installing the Cosworth S2000 Headers

Installing the new headers requires careful alignment, proper gasket placement, and methodical torquing. Rushing this step can lead to exhaust leaks, clearance issues, or damaged components.

Prepare the Headers and Gaskets

  1. Unpack the Cosworth headers and inspect them for any damage that may have occurred during shipping. Check that the flanges are flat, the welds are clean, and the O2 sensor bung is present and properly threaded.
  2. Place the new exhaust manifold gasket onto the cylinder head studs. The gasket is directional; most MLS gaskets have a designated "header side" and "head side." Look for stamped markings or a slight offset in the gasket layers to orient it correctly. If you are unsure, consult the gasket manufacturer's instructions or the Cosworth installation manual.
  3. Apply a thin film of anti-seize compound to the threads of the new header bolts or studs. Avoid getting anti-seize on the gasket or the cylinder head surface, as it can contaminate the sealing area.

Position and Bolt the Headers in Place

  1. Carefully guide the Cosworth headers into position from underneath the vehicle. The equal-length primary tubes may make the header slightly more challenging to maneuver than the factory manifold, so take your time. Tilt and rotate the header to clear the steering shaft, motor mounts, and subframe. On some model years, you may need to disconnect the steering shaft from the steering rack or loosen the motor mount to gain an extra inch of clearance. If the header does not slide into place with moderate effort, recheck your clearances rather than forcing it.
  2. Once the header flanges are seated onto the studs, thread the new nuts onto the studs by hand. Tighten them only finger-tight at this stage. Do not use a ratchet yet; you want the header to remain slightly loose so you can align the collector flange with the rest of the exhaust system.
  3. Attach the collector flange to the catalytic converter or test pipe (if applicable). Use a new gasket at this joint. If the collector flange does not align naturally, loosen the header nuts slightly more and adjust the position of the header until the collector fits squarely against the mating flange. Misalignment at this joint will cause an exhaust leak and may create stress on the header primaries.
  4. With the exhaust system aligned, torque the collector flange bolts or nuts to the manufacturer's specification. For most S2000 exhaust systems, this is typically 30–35 ft-lb. Refer to the specific torque values provided by Cosworth or your exhaust system manufacturer.

Torque the Header Bolts to Specification

  1. Using a torque wrench, tighten the header nuts to the factory specification. For the S2000 F20C and F22C engines, the exhaust manifold nut torque is typically 23–27 ft-lb (31–36 Nm). Always verify this value in the Cosworth product documentation, as aftermarket headers may require a slightly different torque.
  2. Tighten the nuts in a crisscross pattern working from the center studs outward. This pattern ensures even clamping pressure across the gasket and prevents the flange from warping. Do the first pass at 15 ft-lb, then a final pass at 23–27 ft-lb.
  3. Recheck each nut after the final pass to confirm that none have backed off. Then, using a permanent marker, place a small alignment mark on each nut and stud so you can visually verify that the nuts have not loosened during the initial heat cycle.

Reconnect Sensors and Brackets

  1. Thread the primary O2 sensor back into the O2 sensor bung on the Cosworth header. If the header has multiple bungs (some versions include a bung for a wideband sensor), use the one that is closest to the cylinder head for the primary sensor. Apply a small amount of anti-seize to the O2 sensor threads, being careful not to get any on the sensor tip.
  2. Tighten the O2 sensor to 30–35 ft-lb using an O2 sensor socket. Do not overtighten, as this can damage the sensor or strip the threads in the bung.
  3. Reconnect the O2 sensor wiring harness and secure the wire loom away from the header tubes using zip ties or heat-resistant wire separators. The primary tubes will become extremely hot, so ensure the wiring does not contact the metal surfaces.
  4. If you removed the intake manifold or intake ducting, reinstall it at this point. Torque the intake manifold bolts to the factory specification (typically 16–20 ft-lb for the F20C) in a crisscross pattern. Reconnect any vacuum lines, coolant hoses, and electrical connectors that were disconnected.

Post-Installation Checks and First Start

After the headers are installed and all components are reassembled, perform a thorough inspection before starting the engine. Rushing this phase can turn a successful installation into a frustrating troubleshooting session.

Verify Clearance and Fastener Security

  1. Rotate the steering wheel lock-to-lock with the engine off and listen for any contact between the header primary tubes and the steering shaft. If you hear rubbing, loosen the header bolts, reposition the header slightly, and retighten. Even minor contact can cause a loud rattle and may eventually wear through the tubing.
  2. Check that all bolts, nuts, and clamps are present and tightened. Pay special attention to the collector joint, O2 sensor, and any support brackets you reinstalled.
  3. Reinstall the undertray if it was removed. The undertray helps direct airflow through the engine bay and protects the exhaust components from road debris.

Reconnect the Battery and Start the Engine

  1. Reconnect the negative battery terminal. Ensure the connection is clean and tight.
  2. Start the engine and let it idle. The engine may run slightly rough for the first 30–60 seconds as the ECU recalibrates its fuel trims to account for the reduced backpressure. This is normal. Allow the engine to reach operating temperature.
  3. Listen for exhaust leaks at the head flange, collector joint, and any other connections. A ticking or hissing sound that increases with engine speed indicates a leak. If you suspect a leak, use a length of hose or a mechanic's stethoscope to pinpoint the source. Tighten the affected bolts slightly if the leak is minor; if the leak persists, the gasket may be misaligned and will need to be replaced.
  4. With the engine hot, carefully feel around the header flanges for any signs of exhaust gas escape. Do not touch the header tubes directly, as they will be extremely hot. Use a piece of cardboard or a non-contact thermometer to detect hot spots indicative of a leak.

Test Drive and Heat Cycling

  1. Take the vehicle on a short test drive of 10–15 minutes, varying engine speed and load. Listen for any new rattles, vibrations, or exhaust noises. The Cosworth headers should produce a deeper, more aggressive note under acceleration, but there should be no metallic rattling or buzzing.
  2. Allow the engine to cool completely for several hours or overnight. This heat cycle allows the gaskets and flanges to seat properly under thermal expansion and contraction.
  3. After the engine has cooled, re-torque the header nuts to the factory specification. Some settling of the gasket is normal, and a second torque pass ensures a long-lasting seal. This step is critical; skipping it is the most common cause of exhaust leaks that appear weeks after installation.

Tuning and ECU Calibration

While the Cosworth S2000 headers deliver noticeable gains without any ECU modification, the engine will benefit significantly from a proper tune. The factory ECU is calibrated for the stock exhaust system's backpressure characteristics. When you reduce backpressure with aftermarket headers, the engine runs leaner at certain load points, particularly in the mid-to-high rpm range. A lean condition can cause knock, detonation, and reduced power output.

For the best results, consider having the ECU tuned on a dynamometer by a qualified Honda tuner. A flash tune or standalone ECU calibration can optimize the air-fuel ratio, ignition timing, and VTEC engagement point to take full advantage of the improved exhaust flow. Typically, a tuned S2000 with Cosworth headers and a compatible cat-back exhaust system gains 15–25 whp over a completely stock vehicle. Even if you choose not to tune immediately, monitoring air-fuel ratios with a wideband gauge is a wise precaution, especially if you plan to track the car.

For further reading on tuning and calibration strategies for the F20C and F22C engines, refer to resources such as S2Ki and Cobalt FTW for community-sourced dyno data and tuning guides.

Long-Term Maintenance and Care

Stainless steel headers are durable, but they still require occasional attention to maintain their performance and appearance. Follow these best practices to maximize the lifespan of your Cosworth S2000 headers.

Periodic Re-Torquing and Leak Inspection

  • Inspect header bolts for tightness every 3,000 miles during the first year of service. After the initial settling period, check them annually or whenever you perform other under-hood maintenance.
  • Look for exhaust leaks at the head flange and collector joint. A leak can often be detected by the presence of black soot around the gasket area. If you see soot, tighten the adjacent bolts slightly and re-inspect.

Corrosion and Finish Care

  • Stainless steel can develop surface discoloration from heat cycling, which is cosmetic and does not affect performance. If you want to preserve the original appearance, you can polish the headers with a stainless steel cleaner designed for high-temperature applications.
  • In areas where road salt is used, the underside of the vehicle is exposed to corrosive conditions. A light coating of high-temperature exhaust paint or ceramic coating can provide an extra layer of protection. Cosworth headers are sometimes available with a ceramic coating option from the factory, which also helps reduce under-hood temperatures.
  • Keep the exhaust system free of debris such as road grime, oil, and coolant. If you spill fluids on the headers during other maintenance work, clean them promptly to prevent staining.

Gasket Replacement Intervals

The multi-layer steel gasket used on the S2000 can last the life of the vehicle if properly installed and maintained. However, if you ever remove the headers for any reason, always replace the gasket with a new one. The gasket compresses during its initial heat cycle and will not seal properly if reused.

Frequently Asked Questions

Will Cosworth S2000 headers fit both AP1 and AP2 models?

Cosworth manufactures headers that fit both generations, but it is important to confirm the specific part number at the time of purchase. AP1 and AP2 cylinder heads have subtle differences in port geometry, and older AP2 models may have variations in the exhaust flange pattern. Always verify compatibility with Cosworth or your authorized dealer before ordering.

Do I need a tune after installing the headers?

While the engine will run safely on the factory ECU calibration for normal street driving, a tune is strongly recommended to realize the full power potential and to ensure a proper air-fuel ratio across the entire rpm range. A tune also allows you to adjust the VTEC crossover point and ignition timing to match the new exhaust flow characteristics.

How do Cosworth headers affect sound?

The Cosworth headers produce a higher-pitched, more aggressive exhaust note compared to the stock manifold. The equal-length primary tubes create a more harmonic tone, and the reduced backpressure allows the engine to rev more freely. Pairing the headers with a quality cat-back exhaust system produces a distinctive sound that is widely regarded as one of the best among naturally aspirated inline-four engines. For more information on exhaust sound characteristics and S2000 modifications, visit Honda-S2000.com for community reviews and audio clips.

What are the emissions implications of installing aftermarket headers?

In many jurisdictions, replacing the factory catalytic converter with a test pipe or high-flow catalytic converter is not legal for street use. The Cosworth headers themselves do not replace the catalytic converter; they replace the exhaust manifold only. However, if you are using a high-flow cat or a test pipe in conjunction with the headers, check your local emissions regulations before installing them. Some areas require the vehicle to retain a CARB-compliant catalytic converter.

Can I install the headers myself, or should I hire a professional?

A mechanically inclined enthusiast with a complete set of tools and a weekend of free time can install the Cosworth headers in a home garage. The job does not require specialized equipment beyond a torque wrench and jack stands. However, if you are not comfortable working on exhaust systems or do not have access to a lift, hiring an experienced shop can save time and frustration. Installation time typically ranges from three to six hours, depending on your skill level and whether any fasteners are seized.

Final Thoughts

The Cosworth S2000 headers are a well-engineered upgrade that transforms the driving character of the Honda S2000. The installation process requires careful preparation, patience, and attention to detail, but the rewards are lasting: improved throttle response, increased horsepower and torque, and a soundtrack that complements the engine's high-revving nature. By following the steps outlined in this guide, using the correct tools and replacement parts, and taking the time to perform post-installation checks and maintenance, you can complete the installation with confidence and enjoy the benefits of better flow and sound for years to come. For additional technical specifications and official installation resources, refer to the Cosworth official website.