Introduction: Why Upgrade to JDM 370Z Headers?

Upgrading your Nissan 370Z with a set of JDM headers is one of the most effective bolt-on modifications for unlocking genuine horsepower and torque gains. Factory headers are designed for low cost and emissions compliance, often with restrictive cast iron or thin-walled manifolds that choke exhaust flow. JDM aftermarket headers, typically made from mandrel-bent stainless steel with smooth, equal-length primary tubes, reduce backpressure, improve scavenging, and allow the VQ37VHR engine to breathe more freely. Expect gains of 10–20 whp and a broader torque curve when combined with a proper tune and free-flowing exhaust system. This guide provides a detailed, shop-quality walkthrough for a successful JDM header installation on your 370Z.

Before diving in, understand that header installation on a 370Z is an intermediate-to-advanced DIY job. It requires mechanical aptitude, patience, and the right tools. If you’re uncomfortable working with exhaust fasteners, oxygen sensors, and tight engine bay clearances, consider enlisting a professional. However, for those ready to tackle the job, the satisfaction and cost savings are substantial.

Tools and Materials Needed

Having everything on hand before you start prevents frustrating trips to the auto parts store. Here’s a comprehensive list:

  • JDM 370Z headers – Ensure they are designed for your specific model year (09-14 or 15+ with slight variations).
  • Socket set – Standard and deep sockets in 10mm, 12mm, 14mm, 17mm, and 19mm. 6-point sockets are preferred for stubborn bolts.
  • Torque wrench – 3/8” drive for smaller fasteners, 1/2” drive for header bolts (range 20-80 ft-lbs).
  • Jack and jack stands – A low-profile jack and four jack stands to raise and safely support the vehicle.
  • Penetrating oil – WD-40 Specialist or PB Blaster for rusted bolts. Apply 24 hours prior.
  • Exhaust gasket set – High-quality copper or multi-layer steel (MLS) gaskets for header-to-head and header-to-midpipe connections. Do not reuse old gaskets.
  • Gasket maker – High-temp RTV silicone (rated 500°F+) for additional sealing if needed.
  • O2 sensor socket – A 22mm offset or slotted socket to remove oxygen sensors without damaging wiring.
  • Extension bars and universal joint – 6” and 12” extensions plus a swivel adapter to reach awkward bolts.
  • Breaker bar – 24” at minimum for breaking loose corroded nuts.
  • Thread lock compound – Medium-strength (blue Loctite 243) for header bolts.
  • Safety glasses – Protect eyes from debris and dripping fluids.
  • Mechanic’s gloves – Heat-resistant and cut-resistant gloves for grip and safety.
  • Floor creeper (optional but recommended for under-vehicle work).

Preparation Steps

Proper preparation saves time and ensures safety. Follow these steps before lifting the vehicle:

  • Park the 370Z on a flat, level surface. Ensure the engine is completely cool to avoid burns from hot exhaust components.
  • Engage the parking brake firmly. Chock the rear wheels on both sides.
  • Disconnect the battery negative terminal. This prevents accidental shorts and resets the ECU after installation.
  • Soak all exhaust bolts and nuts (header-to-head, header-to-midpipe, O2 sensors, and heat shield fasteners) with penetrating oil. Let it soak overnight for best results.
  • Raise the front of the vehicle using a jack at the front crossmember or subframe jack point. Place jack stands under the factory lift points on the side sills (reinforced by pinch welds). Lower the vehicle onto the stands. For extra clearance, also lift the rear slightly.
  • Remove the under-engine cover (plastic splash shield) held by 10mm bolts and push clips to access the exhaust system.

Removing the Old Headers

With the car safely elevated, begin disassembly. The factory headers are integrated with the primary catalytic converters on the 370Z, making removal more involved than a simple manifold swap. Expect the job to take 3–5 hours on your first attempt.

Step 1: Disconnect the Exhaust Mid-Pipe

Unbolt the mid-pipe from the headers. There are two flanges with two nuts each – one for each side. Use a 14mm socket and extension. If the nuts are seized, apply more penetrating oil and use a breaker bar. Separate the mid-pipe and lower it onto a jack stand or support it with a wire hanger to relieve strain on hangers.

Step 2: Remove Oxygen Sensors

The primary (upstream) O2 sensors are located in the header pipes. Use a 22mm O2 sensor socket to unscrew them carefully. Do not pull on the sensor wires – gently work the sensor out. Place them aside in a clean area. Note: you may need to remove the secondary (downstream) sensors as well if they are integrated with the header assembly; check your specific header design.

Step 3: Unbolt Heat Shields

Remove any heat shields covering the headers. Typically, there are two front shields held by 10mm bolts. Some aftermarket headers do not require reinstallation of these shields, but if your new headers have clearance, you can reuse them for thermal protection of adjacent components.

Step 4: Remove Header-to-Head Bolts

The factory headers are secured to the cylinder head by 10 bolts per side (20 total). These bolts are 12mm hex. Use a deep socket with an extension and universal joint to reach the lower ones near frame rails. Loosen in a cross pattern to prevent warping the flange. Once all bolts are removed, gently tap the header flanges with a rubber mallet to break the gasket seal. Lift the header out from below. On the driver’s side, you may need to remove the engine mount bracket or steering shaft intermediate shaft for clearance. Consult a factory service manual for exact torque specs (typically 35-40 ft-lbs for the header bolts).

Preparing the New JDM Headers

Before installation, inspect the new headers thoroughly. Check for welding defects, cracks, or debris inside the tubes. Clean the flanges with brake cleaner. If your headers are ceramic coated, handle with care to avoid chipping. Prep the installation surfaces:

  • Clean the cylinder head mating surfaces with a scraper and brake cleaner to remove old gasket material. Be careful not to scratch the aluminum head.
  • Apply a thin bead of high-temp RTV gasket maker to both sides of the new header gaskets (if recommended by the gasket manufacturer) – this helps prevent leaks on imperfect surfaces.
  • Install the header gaskets onto the cylinder head studs. Ensure the gasket orientation matches the port shape (some are handed).
  • If your JDM headers include O2 sensor bungs, install the upstream sensors into the new headers at this stage. Use anti-seize compound on the threads (avoid getting it on the sensor tip). Torque O2 sensors to 30-35 ft-lbs.

Installing the New JDM Headers

This is the critical stage. Patience and methodical work pay off.

Step 1: Position and Start Bolts

From under the car, lift the new header into place. It may require angling and rotating to clear the steering shaft (driver’s side) and engine mount. A helper can be invaluable. Once the header flange aligns with the head studs, slide it onto the studs. Start all bolts by hand – do not use a power tool. Apply a drop of blue Loctite to the threads of each bolt. Use the factory bolts if they are in good condition, or the bolts provided with your JDM headers (verify thread pitch and length).

Step 2: Torque Bolts to Spec

Using a 3/8” torque wrench, tighten the header bolts in a crisscross pattern from the center outward. Final torque spec for factory bolts: 38 ft-lbs (some aftermarket headers may recommend 35-40 ft-lbs; always follow the manufacturer’s instructions). Over-torquing can strip head threads or warp the flange. Under-torquing leads to exhaust leaks.

Step 3: Reconnect Mid-Pipe

Align the header flanges with the mid-pipe flanges. Use new gaskets. Apply anti-seize to the nuts. Torque the two nuts per flange to 30-35 ft-lbs. Reinstall any heat shields that clear the new headers.

Step 4: Reinstall Oxygen Sensors

If you removed the downstream sensors, reinstall them into the mid-pipe or header bungs. Torque to spec. Verify all sensor wires are routed away from hot surfaces and moving parts. Secure with zip ties if needed.

Final Steps

After installation, perform these checks and procedures to ensure a successful outcome:

  • Reconnect the battery negative terminal.
  • Start the engine and let it idle for two minutes. Listen for any ticking or hissing sounds indicating exhaust leaks. A small initial smell of burning oil from new coatings is normal.
  • Check for leaks by spraying soapy water around gasket joints (header-to-head and header-to-midpipe). Bubbles indicate a leak – re-torque if needed.
  • Cycle the engine through varied RPMs (do not exceed 4000 RPM until the ECU learns) to promote gasket seating.
  • Lower the vehicle fully after confirming no issues.
  • Test drive gently for 10–15 miles, then re-torque the header bolts one final time after a heat cycle. This is crucial to prevent loosening due to thermal expansion.

ECU Reset and Tuning Considerations

Factory ECU will adapt to the increased airflow but may require a reset for optimal learning. Disconnect the battery for 15 minutes, then reconnect and drive gently for 20-30 miles. For maximum gains, a professional ECU tune (via UpRev, ECUTEK, or a custom dyno tune) is strongly recommended. A tune can advance ignition timing and adjust fuel maps to exploit the free-flowing headers, adding an additional 10–15 hp over a non-tuned setup. Always run high-octane pump fuel (91 or 93) after tune.

Common Pitfalls and Troubleshooting

  • Stubborn bolts: If a header bolt snaps, you’ll need a bolt extractor or time-sert repair. Prevent this by pre-soaking and using a quality breaker bar.
  • Steering shaft interference: On some 370Z models, the steering intermediate shaft rubs against aftermarket headers. Solutions include dimpling the header tube slightly, installing a steering shaft spacer, or using a header with a clearance dent.
  • Check engine light (CEL): A CEL for O2 sensor efficiency (P0420) is common after header install because high-flow cats or catless pipes trigger the monitor. If your JDM headers include high-flow cats, the light may still appear. A tune can disable that monitor or adjust parameters. Alternatively, install O2 sensor spacers (defoulers) to raise the sensor out of the direct exhaust stream.
  • Exhaust smell: Catless headers produce a stronger fuel odor, especially at idle. Consider aftermarket cats if daily driving with emissions testing.

Performance Expectations

With a quality installation and tune, JDM 370Z headers can deliver:

  • Peak horsepower gain: 15–25 whp on a dynojet.
  • Mid-range torque increase: 10–15 lb-ft from 3500-5500 RPM.
  • Improved throttle response and exhaust note – deeper, more aggressive tone.

Gains depend on supporting mods (intake, exhaust, tune). For reference, real-world dyno numbers from 370Z forums show consistent results across multiple brands.

Conclusion

Installing JDM 370Z headers is a rewarding project that elevates your car’s performance and sound. By following this expanded step-by-step guide, you can complete the job safely and effectively, reaping the full benefits of improved exhaust flow. Remember to invest in quality gaskets, torque every bolt to spec, and re-torque after a heat cycle. For further reading, check out Z1 Motorsports’ header installation guide and this detailed video walkthrough that complements our written instructions. Happy wrenching – and enjoy that VQ37VHR roar.