Installing Greddy headers on your Nissan 370Z is one of the most rewarding upgrades you can make to the car’s performance and exhaust note. Greddy has long been respected in the Japanese performance aftermarket, and their 370Z headers are engineered to improve exhaust flow, increase mid-range torque, and deliver a more aggressive, refined sound. However, achieving a perfect fit and getting the results you expect requires careful preparation, proper technique, and attention to detail. This guide provides comprehensive installation tips, troubleshooting advice, and maintenance recommendations to ensure your headers perform flawlessly for years to come.

Preparation Before Installation

Proper preparation saves time, prevents mistakes, and reduces frustration. Before you even jack up the car, gather the right tools, understand the job’s scope, and create a safe workspace.

Tools and Supplies You’ll Need

  • Metric socket set (10 mm, 12 mm, 14 mm, 17 mm) with both shallow and deep sockets
  • Combination wrenches (10 mm, 12 mm, 14 mm, 17 mm)
  • Torque wrench capable of 15–40 ft-lb range
  • Breaker bar or impact wrench for stubborn bolts
  • Oxygen sensor socket (22 mm) if you need to remove sensors
  • Gasket scraper or razor blade
  • Penetrating oil (e.g., PB Blaster or WD-40 Specialist)
  • Anti-seize compound for threads
  • New OEM or high-quality aftermarket gaskets (Greddy headers typically use their own gaskets; check included hardware)
  • Jack stands and floor jack (safely rated for the 370Z’s weight)
  • Shop rags and safety glasses

Important: The 370Z’s engine bay is tight. Removing the intake manifold or disconnecting the intake tube may be necessary to access the lower header bolts. Have a friend handy for extra hands, especially when aligning the headers into position.

Confirm Header Fitment

Greddy manufactures several variations for the VQ37VHR engine. Ensure you have the correct part number for your 370Z model year (2009–2020). Some headers are designed for automatic vs. manual transmissions due to different tunnel clearances. Check the Greddy product page or your invoice before starting.

Check official Greddy header fitment information

Work Environment

Perform the installation in a well-ventilated area—exhaust fumes from engine runs will be present. If using a lift, ensure the car is properly secured. On jack stands, place them under the factory lift points (the pinch welds) and use jack stands rated at least 2 tons per pair. The 370Z sits low; consider using ramps for the front end to improve access without sacrificing ground clearance.

Removing the Old Headers

Removing the factory exhaust manifolds can be the most challenging part of the job, especially if the car has high mileage or lives in a rust-prone region. Follow these steps carefully to avoid broken studs or damage to the cylinder head.

Disconnect the Battery and Sensors

Disconnect the negative battery terminal to prevent short circuits or accidental airbag deployment. Then unplug the primary oxygen sensors (front) from the wiring harness. Use a sensor socket or 22 mm wrench to remove them from the old manifolds. Apply penetrating oil to the sensor threads a day before installation if they appear corroded.

Clear the Work Area

Remove the intake tube and air filter box assembly for better access to the passenger-side manifold. On the driver side, you may need to disconnect the steering shaft heat shield and sometimes the coolant overflow tank bracket. Label any vacuum lines or electrical connectors you disconnect.

Unbolt the Old Manifolds

Start with the exhaust flange bolts connecting the manifold to the mid-pipe. These are often 14 mm nuts and may be corroded; soak them with penetrating oil. Then work on the cylinder head bolts—typically 12 mm or 14 mm nuts on studs. There are 12 nuts per side (six cylinders, two per cylinder). Use a combination of swivel sockets and extensions to reach the lower ones near the firewall.

Pro tip: If a stud comes out with the nut, that’s acceptable as long as you can reinstall it. However, if a stud breaks off in the head, you’ll need a stud extractor or a machine shop for removal. To minimize risk, turn the nuts only after applying penetrating oil and giving it time to work.

Inspect and Clean Surfaces

Once the manifolds are removed, scrape off all old gasket material from the cylinder head mating surfaces. Use a razor blade or a gasket scraper—do not wire-brush aluminum surfaces as this can gouge them. Clean the stud threads with a die or a wire brush. Also clean the exhaust flange where the header connects to the mid-pipe. Replace any damaged studs or nuts.

Find replacement studs, nuts, and gaskets at Z1 Motorsports

Installing the Greddy Headers

Now the rewarding part begins. Greddy headers typically come with new gaskets and hardware. Use them, but also verify that all included bolts match the OEM thread pitch and length.

Prepare the Headers

Before installation, it’s wise to test-fit each header without gaskets. Slide the header onto the studs to check alignment. If the header doesn’t sit flush, you may need to loosen a transmission mount or exhaust hanger to provide a few millimeters of movement. Greddy headers are known for good fitment, but aftermarket variations in engine mounts or subframe bushings can cause minor issues.

Install New Gaskets and Hand-Tighten

Place a new Greddy-supplied gasket (or an OEM gasket if you prefer) over each set of cylinder head studs. Note that Greddy’s gaskets are often multi-layer steel (MLS) and require no additional sealant. Lift the header into position, guiding the primary tubes over the studs. Hand-thread all 12 nuts onto the studs—use a drop of anti-seize on the threads to prevent future corrosion and ensure even torque. Tighten the nuts in a criss-cross pattern from the center outward, working in stages: first all hand-tight, then 15 ft-lb, then final torque to the Greddy specification (typically 30–35 ft-lb for the head nuts).

Connect the Mid-Pipe Flange

With the header bolted to the head, attach the exhaust mid-pipe to the header’s collector flange. Use a new gasket (copper or high-temperature composite) and tighten the two bolts evenly. A flexible mid-pipe section (if your system includes one) helps eliminate binding and stress on the header welds.

Reinstall Oxygen Sensors

Apply anti-seize to the oxygen sensor threads (only the threads, not the tip) and thread them into the provided bungs. Greddy headers usually have bungs for the front O2 sensors; if your car is equipped with secondary O2 sensors for emission monitoring, there may be additional bungs behind the collector. Install them and torque to 30 ft-lb (or as specified).

Driver-Side Clearance Note

The driver-side header often passes very close to the steering intermediate shaft. Some Greddy headers include a heat shield or you can repurpose the OEM heat shield. Check that there is at least ¼ inch clearance through the full steering range. If the header contacts the shaft, you may need to slightly dimple the header tube (a last resort) or adjust the shaft position using washers. Most installations clear with no interference.

See community discussions about clearance issues on The370Z.com

Post-Installation Checks

After everything is bolted up, it’s crucial to verify proper operation before taking the car on the road.

Reconnect Battery and Sensors

Reconnect the negative battery terminal and plug in all O2 sensor connectors. Double-check that no wires are pinched between the header and the engine, or resting on a hot tube. Use zip ties to secure any loose wiring away from the headers.

Start the Engine and Inspect for Leaks

Start the engine and let it idle. Listen for ticking sounds that indicate an exhaust leak at the cylinder head or flange. Spray a soapy water solution (or use a shop vacuum with a smoke machine) around the header joints and watch for bubbles. A minor leak may seal after the gaskets heat-cycle a few times, but a significant leak requires immediate retorquing.

Allow the engine to reach operating temperature (around 190–200°F for the VQ37VHR). Then carefully check the header tubes for any discoloration (bluing) that might indicate a lean condition, although this is rare with a proper tune. The exhaust note will be deeper and louder—this is normal. If you hear a metallic rattle, check heat shields and clearances.

ECU Relearn and Test Drive

After changing exhaust components, the ECU needs to adapt to the new airflow. Perform a throttle relearn procedure: turn ignition ON (not start) for 3 seconds, press accelerator pedal fully and release 5 times quickly, then turn ignition OFF. Start the engine and let it idle for 10 minutes without touching the gas. Then take the car for a gentle drive, varying RPMs through the first 50 miles. Avoid wide open throttle until the ECU fully adapts.

Monitor the temperature. If the car runs hotter than usual, check for any exhaust leak near the cylinder head that could affect the upstream O2 sensor readings.

Maintenance Tips for Longevity

Greddy headers are built from 304 stainless steel and should last the life of the car if maintained properly. However, high heat cycles and road debris can take a toll.

  • Retorque after 500 miles: Due to gasket compression and thermal expansion, check all header nuts and flange bolts after about 500 miles. Tighten to spec.
  • Inspect for cracks: Stainless steel can crack under extreme heat if the fitment causes stress. Look for hairline cracks near welds, especially on the primary-to-collector junctions.
  • Keep headers clean: Ceramic coating (if your Greddy headers are coated) helps shed heat and resist corrosion. Wash the undercarriage regularly in winter to remove salt. If uncoated, consider a high-temperature paint touch-up if rust appears.
  • Oxygen sensor replacement: The headers’ increased flow may cause the upstream O2 sensors to age faster. Replace them every 60,000 miles to maintain accurate air-fuel ratios.
  • Check for exhaust leaks annually: A soapy water spray test takes ten minutes and can catch small leaks before they become major problems.

Sound and Performance Expectations

Greddy headers are designed to improve exhaust scavenging, which reduces backpressure and allows the engine to breathe more freely at higher RPM. On the 370Z, you can expect gains of 10–15 horsepower at the wheels when paired with a cat-back exhaust and a tune. Torque increases are most noticeable in the 3,500–6,500 rpm range, making the car feel stronger during highway passing and canyon runs.

Sound is subjective but almost universally praised. The VQ37VHR’s flat-plane-crank-like roar becomes more pronounced, with a raspy growl above 4,000 rpm. Greddy headers tend to produce a slightly higher-pitched tone compared to long-tube competitors, which some enthusiasts prefer for a “race car” note. If you keep the factory catalytic converters or use high-flow cats, the volume increase is moderate; with a full test-pipe setup, it can be loud enough for track use.

Listen to Greddy header sound clips on YouTube

Troubleshooting Common Issues

Header Hits the Steering Shaft

If you notice contact at full steering lock, loosen the header bolts, shift the header slightly toward the engine, and retighten. Permanent clearance can be created by adding a 1–2 mm spacer between the steering shaft bracket and the frame—just ensure the shaft angle remains safe.

Check Engine Light (CEL) After Installation

A CEL is common if you removed catalytic converters or installed headers without a tune. The rear O2 sensors will trigger a P0420/P0430 code (catalyst efficiency). To resolve, either install O2 sensor spacer (mini-cat) or get a custom ECU tune that disables rear O2 monitoring. Many tuners recommend a proper tune to maximize power and fuel economy.

Exhaust Leak at Header-to-Midpipe Joint

This is often caused by mismatched diameters or a misaligned exhaust system. Use a flexible gasket designed for slip-fit connections. If the mid-pipe doesn’t align, loosen all exhaust hangers and adjust the whole system rearward. Sometimes the aftermarket mid-pipe needs a slight bend—worth consulting an exhaust shop.

Final Tips for a Perfect Install

Take your time. The 370Z’s engine bay is tight, and rushing leads to stripped threads or missed alignment. Work with a buddy to hold the header in place while you start bolts. Use anti-seize on every nut and bolt that will be exposed to exhaust heat—it makes future removal much easier. If you are not comfortable with tuning or mechanical work, consider having a reputable shop install the headers and tune the car on a dyno for optimal results.

With patience, the right tools, and these tips, your Greddy headers will deliver a perfect fit, an incredible sound, and a noticeable performance improvement that transforms your 370Z driving experience.

View Greddy’s installation guide and product details