The HKS Premium Metal S2000 Headers represent a definitive upgrade for the Honda S2000, offering a compelling blend of material excellence, measurable performance gains, and a refined exhaust note. Designed as a direct bolt-on replacement for the restrictive factory exhaust manifold, these headers are engineered to maximize the F20C and F22C engine’s potential. For enthusiasts seeking not just numbers on a dyno but a visceral connection to their car, the HKS Premium Metal headers deliver both at a level that justifies their premium positioning. This article provides a comprehensive look at the construction, performance characteristics, sound profile, installation, and real-world benefits of these headers, helping you decide if they belong under your S2000.

Material Quality and Construction

The foundation of any performance header is its material and build quality. HKS has long been a benchmark in Japanese performance parts, and the Premium Metal S2000 headers are no exception. They are constructed from high-grade stainless steel, specifically chosen for its ability to withstand the extreme thermal cycles of a high-revving four-cylinder engine.

Stainless Steel Grade and Durability

HKS uses SUS304 stainless steel, a common but high-quality choice for performance exhaust components. SUS304 offers excellent corrosion resistance, making it suitable for street-driven cars even in humid or road-salt environments. Unlike mild steel headers that can rust from the inside out, SUS304 maintains its structural integrity over years of use. The material also exhibits good formability, allowing HKS to create complex mandrel-bent tubes without compromising wall thickness.

  • Heat cycling tolerance: SUS304 handles repeated expansion and contraction without cracking, a common failure point on cheaper headers.
  • Wall thickness: Typically 1.5mm to 2.0mm, striking a balance between weight savings and durability to resist warping under heat.
  • Weld quality: HKS employs robotic TIG welding for consistent, clean beads that ensure leak-free joints and long-term reliability.

Mandrel Bending and Flow Path

Mandrel bending is crucial for maintaining consistent inner diameter throughout the header’s primary tubes. The HKS headers utilize mandrel bends to minimize turbulence and backpressure, allowing exhaust gases to exit the cylinder head as efficiently as possible. Smooth, gradual bends reduce restriction, directly contributing to the horsepower gains seen on the dyno. The primary tubes are sized to complement the S2000’s engine displacement and RPM range—not too large to sacrifice velocity at low RPM, but large enough to flow sufficient volume at high RPM.

Performance Gains: Horsepower and Torque

Upgrading to HKS Premium Metal headers yields tangible performance improvements. While exact figures depend on the specific year of the S2000 (AP1 vs AP2) and supporting modifications, independent testing consistently shows gains in the 8–12 horsepower range and similar torque improvements across the mid-to-high RPM band.

Dyno-Proven Results

Many S2000 owners report peak gains of 8–10 whp with a corresponding 6–8 lb-ft torque increase when pairing these headers with a quality cat-back exhaust and a tune. The design prioritizes exhaust gas velocity to reduce turbo-style lag on naturally aspirated engines. The power curve becomes noticeably broader from 4,000 RPM to redline, making the car more responsive during spirited driving.

  • Midrange torque: A flatter torque curve improves driveability in day-to-day scenarios and on track.
  • Peak horsepower: The headers help the engine breathe more freely, unlocking top-end potential often restricted by OEM catalytic converter and manifold design.
  • Throttle response: Improved scavenging effect reduces the time between pedal input and engine reaction, especially beneficial in corner exit situations.

Optimizing Exhaust Flow

The HKS headers feature a tri-Y design—a configuration where primary tubes are paired before merging into the collector. This design helps maintain exhaust pulse separation, improving scavenging efficiency at certain RPM ranges. The collector is smoothly merged to a 2.5-inch outlet, matching common aftermarket test pipes or downpipes. Combined with the material quality, this engineering yields consistent, repeatable performance gains across different S2000 examples.

Sound Profile Characteristics

The auditory experience of the S2000 is a major part of its appeal. The HKS Premium Metal headers produce a deeper, more aggressive tone compared to the stock manifold without becoming overwhelmingly loud or droning. The sound profile is purposeful and sporting, complementing the car’s character.

Deep and Aggressive Note

At idle and low RPM, the exhaust note takes on a lower, more growling character. As revs climb past 5,000 RPM, the sound transitions into a sharper, more intense scream that is distinctively Honda VTEC. The tri-Y design helps reduce the harshness sometimes associated with four-into-one headers, resulting in a more mature and refined tone.

  • No drone: HKS engineers have tuned the primary lengths to minimize in-cabin resonance in common cruising RPM ranges (3,000–4,000 RPM).
  • Volume increase: Expect a moderate increase in overall volume—about 15–20% louder than stock, depending on the rest of the exhaust system.
  • Compatibility with other systems: These headers pair exceptionally well with HKS’s own cat-back or other aftermarket options like the Invidia Q300 or ARC titanium systems.

Balancing Sound and Daily Use

Because the headers retain a catalytic converter in the factory location (unless you choose a test pipe), emissions compliance and noise levels remain reasonable for daily driving. The sound is sporty enough to be engaging but not so loud as to attract unwanted attention or cause fatigue on long drives. Enthusiasts seeking even more aggression can pair the headers with a high-flow cat or test pipe, transforming the car’s personality without excessive drone.

Design and Engineering Excellence

HKS’s reputation is built on decades of R&D, and the Premium Metal headers showcase their engineering depth. Beyond material and sound, the design incorporates several thoughtful features that make installation easier and performance more consistent.

Primary Tube Length and Diameter

The primary tubes are designed to specific lengths—typically around 32–34 inches—to optimize torque production in the upper half of the RPM range. Each tube is equal-length to ensure balanced flow from all four cylinders, improving the scavenging effect and reducing exhaust pulse interference.

The diameter of the primary tubes is a moderate 1.75 inches. This is a proven size for naturally aspirated Honda F20C engines, supporting both high RPM power and decent midrange torque. Larger diameters (like 2 inches) may shift the power band too high for street use; smaller diameters would restrict top-end flow. HKS has struck a careful balance.

Flange Design and Gasket Compatibility

The header flange that bolts to the cylinder head is CNC-machined from 12mm thick stainless steel, ensuring a flat sealing surface that resists warping. The flanges are precision-cut to match the OEM port layout, allowing reuse of factory manifold gaskets or upgrading to multi-layer steel (MLS) gaskets for a better seal under high boost or extreme heat. The collector flange is also thick, preventing leaks at the junction with the catalytic converter or test pipe.

Installation Process and Tips

Installing HKS Premium Metal headers on the S2000 is a moderate DIY project. Most experienced enthusiasts can complete the job in 3–5 hours with basic hand tools, but patience is required, particularly when dealing with the lower studs and oxygen sensors.

Step-by-Step Installation Overview

  1. Disconnect the battery and allow the engine to cool completely. Working on a hot exhaust manifold is dangerous and can cause burns.
  2. Remove the factory heat shield, followed by the three nuts securing the exhaust manifold to the head. Also loosen the nuts at the exhaust pipe connection and the rear engine mount bracket if interfering.
  3. Disconnect the oxygen sensors (primary and secondary). Use a wire brush and penetrating oil if they are seized.
  4. Carefully extract the stock manifold. It helps to unbolt the rear engine mount and tilt the engine slightly for clearance.
  5. Install the new HKS headers with new gaskets. Tighten in a crisscross pattern to 28–32 Nm (20–24 lb-ft) per the Honda service manual. Do not overtighten as stainless steel is less forgiving than cast iron.
  6. Reattach the downstream connections and oxygen sensors. Use anti-seize on the O2 sensor threads to ease future removal.
  7. Double-check all bolts, clearance to the chassis, and ensure no contact with the steering shaft or crossmember.
  8. Start the engine and check for exhaust leaks. Let the car idle until the cooling fans cycle once, then test drive.

Important Considerations

  • Oxygen sensor extensions: Some aftermarket headers relocate the primary O2 sensor boss; HKS headers typically maintain the stock location, but extensions may be needed if using certain test pipes.
  • Torque specifications: Always follow the manufacturer’s recommended torque values. Stainless steel can gall, so using a torque wrench is essential.
  • Professional installation: If you are unfamiliar with exhaust systems or working on the S2000’s tight engine bay, professional installation is advised. Labor costs are typically $200–$400.

Maintenance and Longevity

With proper care, HKS Premium Metal headers can outlast the car itself. Their corrosion-resistant stainless steel construction minimizes maintenance, but a few practices will keep them looking and performing their best.

  • Periodic inspection: Check the flange bolts and collector nuts every 5,000 miles or after any track day. Heat cycling can loosen fasteners over time.
  • Cleaning: If you drive in winter conditions, rinse the underside occasionally to remove road salt. For aesthetic purposes, stainless steel polishes work well, but avoid abrasive pads that can scratch.
  • Gasket replacement: Replace the manifold gasket every time you remove the headers. MLS gaskets are recommended and relatively inexpensive.
  • Heat wrapping: While not necessary, wrapping the primary tubes with heat wrap can reduce underhood temperatures and help maintain exhaust gas velocity. However, some wraps trap moisture and may accelerate corrosion on non-stainless components.

Comparing HKS to Other Performance Header Options

The S2000 aftermarket offers several header choices, from budget-friendly brands to high-end titanium units. The HKS Premium Metal headers sit in the upper-middle tier, offering a strong value proposition.

OEM Manifold vs HKS

The stock cast-iron manifold is heavy, restrictive, and prone to cracking with age. Its flow characteristics are a major bottleneck for any performance build. Switching to HKS headers immediately reduces weight (by approximately 6–8 pounds) and liberates power that is otherwise trapped.

HKS vs Toda Racing Headers

Toda Racing headers are known for their competitive lightweight construction and aggressive tuning. Their four-into-one design often sacrifices some midrange torque for top-end power. The HKS tri-Y design provides a broader power band, making it a better choice for street-driven cars that still see occasional track use. HKS also tends to be slightly more affordable than Toda’s offering.

HKS vs Mugen Exhaust Manifold

Mugen’s header is designed with similar principles of quality and fitment, but it often commands a higher price due to brand exclusivity. HKS offers comparable performance and superior availability. For most enthusiasts, the HKS unit represents a better performance-per-dollar ratio.

HKS vs Budget Headers (e.g., Megan Racing, Skunk2)

Budget headers are significantly cheaper but often come with compromises: thinner flanges that warp, inconsistent weld quality, and narrower tubes that may restrict flow. The HKS headers justify their price with superior fitment, better materials, and proven performance. A budget header might save $300–$500 initially but could require replacement or repair after a few years, negating the savings.

Frequently Asked Questions

Will HKS S2000 headers pass emissions?

Yes, when paired with a functioning primary catalytic converter. The headers themselves do not contain a catalytic converter; they replace the exhaust manifold. As long as you retain a high-flow or factory cat in the exhaust system, the car should pass emissions in most states. Removing the cat entirely will likely cause a failure and trigger the check engine light.

Do I need a tune after installing these headers?

While the engine management can adapt to some extent, tuning is highly recommended to fully realize the performance gains. The stock ECU may not adjust timing and fueling aggressively enough to take advantage of improved flow. A flash tune or a standalone ECU can unlock an additional 5–10 horsepower and ensure safe air-fuel ratios.

How does the sound change with a cat-back exhaust?

Pairing HKS headers with a cat-back system creates a significantly more aggressive exhaust note. The sound becomes louder and more visceral, especially under VTEC crossover. Most enthusiasts find the combination exhilarating and not excessively loud for daily driving, but it may attract attention.

Are HKS headers compatible with AP1 and AP2 models?

HKS typically offers separate part numbers for AP1 (2000–2003) and AP2 (2004–2009) models due to differences in the cylinder head flange and chassis mounting points. Always verify compatibility with your specific year before purchasing. Reputable retailers like Evasive Motorsports or Science of Speed can confirm fitment.

Final Verdict: Are HKS Premium Metal S2000 Headers Worth It?

For any Honda S2000 enthusiast dedicated to extracting the car’s full potential—whether on back roads, autocross, or track days—the HKS Premium Metal headers are an outstanding investment. Their meticulous construction from high-grade stainless steel ensures long-term durability in harsh conditions. The performance gains, while not revolutionary on a stock engine, are meaningful and consistent, particularly when combined with a tune and free-flowing exhaust. The sound profile strikes a near-perfect balance between aggression and daily livability, avoiding the drone and rasp common to lesser headers.

While the price is higher than budget alternatives, the fitment, reliability, and engineering pedigree justify the cost. HKS has refined this design over years of racing and street application, resulting in a product that bolts on without hassle and delivers predictable results. Whether you are building a dedicated track car or simply want to enjoy a more responsive, better-sounding S2000, the HKS Premium Metal headers should be near the top of your shopping list.

For additional technical reading on header design principles, see EngineLabs’ header design basics and the official HKS product page for the S2000 line.