Why Upgrade the Headers on Your 370Z?

Swapping the factory exhaust manifolds for aftermarket headers is one of the most effective bolt-on modifications for the Nissan 370Z. The VQ37VHR engine responds well to reduced exhaust restriction, unlocking higher peak horsepower and a broader torque curve. Additionally, the sound becomes deeper with more pronounced engine notes, especially in the upper rev range. While the process is more involved than a cat-back exhaust, a DIY installation is achievable with the right tools, patience, and proper preparation. This guide provides detailed steps and pro tips to help you complete the job cleanly and avoid common pitfalls.

Understanding Header Designs for the 370Z

Headers replace the restrictive cast-iron manifolds with individual tubes for each cylinder. The design options affect installation complexity, performance, and sound:

Long Tube vs. Shorty Headers

Long tube headers replace the entire exhaust from the cylinder head to the catalytic converter location. They offer the largest power gains by scavenging exhaust pulses more effectively, but require removal of the factory cats and often a custom midpipe or test pipes. They also complicate emissions compliance in strict states. Shorty headers bolt directly to the factory Y-pipe, making installation simpler and retaining the stock catalyst setup. Gains are moderate (5–10 hp) versus 15–20+ hp for long tubes, but shorties are easier to install and emissions-friendly.

Equal vs. Unequal Length

Equal-length headers optimize scavenging by making each cylinder’s path the same length, producing a smooth exhaust note and maximum power. Unequal-length headers create a classic “boxer rumble” but often sacrifice a few horsepower. Most 370Z aftermarket headers are equal-length for best performance.

Material Choices

Mild steel headers (e.g., stock replacement) are inexpensive but prone to rust. Stainless steel (304 or 316 grade) resists corrosion and heat cycles, making it the preferred choice for long-term use. Ceramic-coated headers reduce underhood heat, lower intake temperatures, and improve thermal efficiency. Expect to pay $400–$1,200 depending on brand and coating.

Tools and Materials: What You’ll Need

Beyond a basic socket set, the 370Z’s tight engine bay demands specialized items for a smooth removal. Gather these before starting:

  • 1/2” drive ratchet, extensions (3”, 6”, and 12”) and universal swivel sockets
  • Deep sockets: 10mm, 12mm, 14mm, 17mm (for header bolts and O2 sensors)
  • Combination wrenches (12mm, 14mm, 17mm) and a 5mm hex bit (for some header designs)
  • Oxygen sensor socket (22mm) and an O2 sensor spacer (if needed to avoid CEL)
  • Torque wrench (0–100 ft/lb range)
  • Breaker bar (18” or longer) for stubborn bolts
  • Floor jack and two jack stands (minimum 3-ton capacity)
  • Penetrating oil (e.g., PB Blaster or Kroil)
  • High-temp anti-seize compound (copper or nickel-based)
  • New header gaskets (copper or multi-layer steel)
  • Thread-locker (medium strength for studs, if used)
  • Safety glasses, mechanic gloves, and shop rags

Optional but recommended: A creeper, a headlamp, and a mirror on a stick for inaccessible bolts. A 19mm swivel socket also helps reach the lower exhaust flange nuts.

Preparing the 370Z for Header Removal

Proper prep prevents damaged hardware and unnecessary trips to the parts store. Block off at least half a day for a first-time install.

  • Park on a level surface, chock the rear wheels, and let the engine cool completely (overnight is best). Exhaust components reach high temps and can cause burns.
  • Disconnect the negative battery terminal to avoid shorting sensors or triggering airbag systems.
  • Spray penetrating oil on all header-to-head bolts, O2 sensor threads, and exhaust flange nuts. Wait 15–20 minutes for the oil to work.
  • Jack up the front of the car and place jack stands under the front frame rails (not the crossmember). Ensure the car is stable before crawling underneath.
  • Remove the under-engine splash shield (Phillips screws and 10mm bolts).
  • Disconnect the front O2 sensors’ electrical connectors (located near the intake manifold). Pull the sensor wire clips and label them driver/passenger side for reassembly.

Removing the Air Intake and Heat Shields

On the passenger side, the intake tube and air box block access to the header. Remove the intake tube (clamp at throttle body and MAF sensor) and the air filter box (two 10mm bolts). For the driver side, you may need to unbolt the upper radiator hose bracket for clearance. Use a small screwdriver to release factory heat shield tabs; these shields often break, so plan to replace them with aftermarket heat wrap if needed.

Removing the Stock Manifold: Step-by-Step

The 370Z’s stock manifolds are heavy, single-piece cast iron. Lifting them out requires careful maneuvering.

  1. Disconnect the Y-pipe from the manifolds. Unbolt the two spring nuts at each manifold’s outlet (17mm). If they are rusted, use a breaker bar and penetrating oil. Remove the gaskets (they often stick and tear).
  2. Remove the front O2 sensors using the 22mm socket. Important: Clean the sensor threads before removing to avoid damaging the sensor. If stuck, apply heat from a torch for 30 seconds.
  3. Unbolt the manifold from the cylinder head. There are 12mm bolts (some 14mm on later years) arranged in a circle. Access is tight: use a swivel socket and extensions to reach the rear bolts. Loosen in a cross pattern to prevent head distortion.
  4. Lift the manifold out. On the driver’s side, you may need to lower the steering shaft (two 12mm bolts) for clearance. On the passenger side, lift the manifold upward while tilting it toward the firewall. A second set of hands helps avoid damaging the O2 sensor wires or studs.
  5. Clean the head surface with a plastic scraper. Remove all gasket residue. Avoid scratching the aluminum head. Clean the bolt threads with a tap (M10x1.25 for 12mm bolts) to remove old thread sealer.

Pro tip: Some stock manifold nuts will snap. Have a few M10x1.25 flanged hex nuts and bolts on hand from the hardware store.

Installing the New Headers

Before bolting up, test-fit the header to the cylinder head. Many aftermarket headers require slight trimming of the crossmember heat shield or shifting the steering shaft. Do not force anything.

  1. Apply anti-seize compound to the header bolt threads and also to the O2 sensor threads (use a copper-based anti-seize for sensors). Do not get anti-seize on the gasket surfaces.
  2. Install new header gaskets onto the studs (if studs are used; otherwise lay them on the head). Some gaskets are the same on both sides; others are handed. Verify orientation.
  3. Position the header from below. Gently lift it into place while guiding the header primary tubes into the ports. Use a floor jack padded with a rag to support the header’s collector, then adjust height.
  4. Hand-tighten all header bolts until snug. Do not torque yet. Use a 3/8” ratchet to avoid overtightening.
  5. Attach the collector to the Y-pipe (or test pipe, if applicable). Use the factory spring bolts or aftermarket supplied flanges. Snug them hand-tight.
  6. Torque header bolts in sequence (inner to outer, crosswise) to the manufacturer’s specification. Typically 18–22 ft/lb for 12mm bolts, 25–30 ft/lb for 14mm. Over-torquing can warp the header flange or break studs.
  7. Reinstall the O2 sensors. Apply anti-seize, thread them into the header bungs hand-tight, then torque to 25–30 ft/lb. For aftermarket headers, you may need an O2 sensor spacer (angled or straight) to keep the rear sensor out of the exhaust stream and prevent a P0420 code.

Common Clearance Issues

Aftermarket headers often contact the steering shaft (driver side) or the radiator hose (passenger side). Use a pry bar to gently tweak the hose bracket, or wrap the steering shaft with a heat shield sleeve. Do not allow metal-to-metal contact as it will transmit vibration and noise.

Reassembling the Exhaust and Intake Systems

Once the headers are secure, reverse the removal steps:

  • Reconnect the Y-pipe or test pipes. Use new gaskets at all exhaust joints. Tighten bolts to 35–40 ft/lb.
  • Reinstall the air intake tube, filter box, and MAF sensor. Ensure all clamps are tight and the MAF sensor is oriented correctly (arrow pointing toward engine).
  • Reattach heat shields (if reusing) or apply thermal wrap to the headers. If wrapping, do it before installation.
  • Reconnect the O2 sensor connectors and secure any loose wiring with zip ties away from the headers.
  • Lower the vehicle carefully, then reconnect the battery.

Important: Check that all electrical connections are firmly seated. A loose O2 sensor will throw a trouble code within a few miles.

Final Checks and Testing

Do not rush the startup procedure. Follow these steps to ensure the installation is leak-free and safe.

  1. Turn the key to ON (without starting) for 10 seconds to prime the fuel system.
  2. Start the engine and let it idle. Expect higher idle speed initially (cold start). Listen for ticking or exhaust hissing sounds that indicate a leak at the head or collector.
  3. Let the engine reach operating temperature. Check for leaks using your hand (feeling for puffs of air) or a piece of paper held near joints. A proper exhaust spray (Wurth or equivalent) can also highlight leaks.
  4. Shut off the engine, let it cool for 20 minutes, and retorque the header bolts. The heat cycle may require a slight retightening (1/8 turn) to maintain gasket crush. Do not overdo it.
  5. Take the car for a short test drive (5–10 miles) at varying RPMs. Listen for rattles from contact with the chassis or steering shaft. If you hear contact, adjust the header or add spacing.
  6. After the test drive, let the engine cool and inspect all bolts again. Recheck the O2 sensor wiring routing.

Aftercare: Expect a temporary check engine light if your car has the factory downstream sensors. This is common after header swaps. A professional tune (via ECUTek, UpRev, or Osiris) will recalibrate the air/fuel ratios and disable the rear O2 monitors, providing the full performance benefit and eliminating the CEL.

Considerations Before You Start

Emissions and legality

Long tube headers remove the primary catalytic converters (mounted in the stock Y-pipe) and are illegal for road use in California and many other states. Shorty headers retain the factory cats and are typically emissions-legal. Check local regulations before purchasing.

Sound increase

Headers dramatically increase exhaust volume, especially when combined with a cat-back system. If you want a subtle upgrade, pair shorty headers with the stock muffler; if you want a race-car growl, long tubes plus a straight-through exhaust create an aggressive note.

Need for a tune

While not strictly required for shorty headers (the ECU can compensate within limits), a custom tune maximizes the gains. For long tube headers, a tune is essential to correct air/fuel ratios and disable downstream O2 sensor checks. Expect to pay $400–$800 for a mail-in or dyno tune.

For more detailed information, consult Z1 Motorsports for header options and installation videos, and the The370Z.com forum for owner experiences with specific brands like Fast Intentions, Stillen, or HKS.

Troubleshooting Common Header Installation Issues

  • Exhaust leak at the head: Usually caused by a bent flange or insufficient torque. Remove the header, check flange flatness with a straightedge, and use a new gasket. If the flange is warped, have it machined flat.
  • Check engine light P0420/P0430: Indicates catalytic converter efficiency below threshold. Install O2 sensor spacers (aka “anti-foulers”) on the rear sensors, or get a tune that disables them.
  • Rattling under acceleration: Header tubes contacting the steering shaft, frame rail, or motor mount. Use a pry bar to create a small gap or wrap hot spots with header wrap. Do not dimple the tubes—this reduces flow.
  • Broken studs: If a cylinder head stud snaps, use a stud extractor or weld a nut onto the broken piece. Install new studs with thread locker and anti-seize on the nut side.

Conclusion

Installing headers on a Nissan 370Z is a challenging but rewarding project that provides a noticeable seat-of-the-pants gain. By taking the time to prepare the work area, using the correct tools, and following a careful torque procedure, you can achieve a leak-free installation that sounds and performs beautifully. Remember to bring fresh gaskets, plenty of patience, and a willingness to crawl around the engine bay. Once complete, your 370Z will rev freer, pull harder, and turn heads every time you hit the throttle.