How to Install Test Pipes on a Nissan 350Z – Step-by-Step Guide

Thinking about giving your 350Z a louder, freer-breathing exhaust note? Swapping out the stock catalytic converters for test pipes is one of the first mods many 350Z owners tackle—and for good reason. Not only do test pipes help the engine flow better, but they also give your VQ35DE that raw, aggressive tone it deserves.

In this guide, we’ll show you exactly how to install test pipes on a 350Z, step by step. Whether you’re in your garage with basic tools or just doing your homework before the job, this walkthrough covers everything you’ll need—tools, tips, and the common issues to watch out for.

What Are Test Pipes and Why Install Them on a 350Z?

Test pipes are straight-through pipes that replace your OEM catalytic converters. They reduce exhaust restriction, allowing your VQ35 engine to breathe and rev more freely.

Many 350Z owners install test pipes for:

• Improved throttle response

• Increased exhaust volume

• Small gains in horsepower and torque

However, test pipes are not emissions-legal in many states. They can also trigger the Check Engine Light (CEL) due to rear O2 sensor readings.

When paired with a full exhaust system, high-quality test pipes can deliver an increase of around 6–10 horsepower by improving exhaust flow and reducing backpressure.

Tools and Parts You'll Need

Before starting the installation, gather everything you need:

Essential Tools:

• Penetrating lubricant

• Ratchet and socket set (preferably ⅜” drive)

• Oxygen sensor socket

• Breaker bar or torque wrench

• Jack and jack stands or ramps

Optional Tools:

• O2 sensor extenders (defoulers)

• Anti-seize compound

• Heat gun or torch (for stubborn bolts)

Parts Required:

• Flashark Nissan 350Z Test pipes

• New gaskets

• Replacement exhaust bolts and nuts

Preparation Before You Begin

Working under your car requires safety and planning.

Start by parking the 350Z on level ground. Let the engine cool completely. Then spray penetrating oil on all exhaust bolts—especially those connecting the stock cats to the headers. Let the oil soak for several hours or overnight.

Disconnect your battery to prevent sensor errors while removing O2 sensors. This is a small step that can save you from triggering fault codes.

Step-by-Step Test Pipe Installation for 350Z

Installing test pipes isn’t overly complicated, but it does require patience, the right tools, and a safe workspace. Below is a detailed breakdown of each step in the process. If you're doing this for the first time, take your time and double-check everything along the way.

Step 1: Lift the Car

Use ramps or a hydraulic jack with jack stands to safely raise and support the vehicle. Never work under a car supported by a jack alone.

Step 2: Disconnect Oxygen Sensors

Locate and unplug the O2 sensors connected to the catalytic converters. Use an oxygen sensor socket to loosen and remove them. Be gentle—these sensors are fragile and expensive to replace.

Step 3: Remove the Factory Cats or Y-Pipe

Unbolt the OEM catalytic converters. Some bolts may be rusted or seized, especially on older 350Zs. A heat torch or breaker bar helps with stuck hardware.

Keep the old gaskets and bolts only if they are in good condition, but replacement is recommended.

Step 4: Install the New Test Pipes

Align your test pipes with the flanges and insert fresh gaskets between the joints. Insert the bolts and hand-tighten them first. Then torque everything to spec.

Make sure both sides are evenly aligned and not in contact with the frame or underbody.

Step 5: Reinstall the O2 Sensors

Thread the oxygen sensors into the new test pipes. If you're not using a tuned ECU, you may want to install O2 extenders (defoulers) to prevent CEL.

Reconnect the sensor harnesses after tightening the sensors.

Step 6: Double-Check Everything

Check that all bolts are tight and no gaskets are pinched. Lower the car, reconnect the battery, and start the engine.

After Installation: What to Watch For

Start the car and listen for exhaust leaks or rattling. If you hear a ticking sound, recheck the flanges and gasket seals.

Drive normally for a few days. You may notice a louder, deeper tone and slightly improved throttle feel.

However, if the Check Engine Light comes on, it’s likely due to the rear O2 sensors. You can:

• Install O2 sensor defoulers

• Use a tuned ECU

• Ignore the CEL (not recommended)

Common Issues During Test Pipe Installation

Even with planning, issues can happen. Here are the most common ones:

• Seized bolts – Often caused by heat and corrosion. Heat and PB Blaster help loosen them.

• Broken studs – Especially common on older vehicles. You may need to drill them out or visit a shop.

• O2 sensor damage – Always remove them carefully and avoid using impact tools.

• Misalignment – Can cause exhaust leaks or banging sounds under the car.

Final Thoughts

Installing test pipes on a 350Z can dramatically improve exhaust sound and performance. It's a satisfying project for the hands-on enthusiast.

While the job is doable with basic tools, it does require patience—especially when dealing with rusted bolts or sensors. Always prioritize safety, and remember that test pipes are not legal for street use in all areas.

If you're new to working on cars, consider having a friend help, or consult a professional.