What Are GrimmSpeed WRX Headers?

GrimmSpeed has built a strong reputation in the Subaru aftermarket world for precision-engineered components, and their WRX headers are no exception. These equal-length headers are designed specifically for the turbocharged EJ and FA engine families found in the Subaru WRX and STI. Unlike the unequal-length stock manifolds that produce the classic Subaru rumble, GrimmSpeed's equal-length design prioritizes even exhaust pulse distribution, which allows the turbocharger to spool more efficiently. The result is a header that delivers measurable performance gains while maintaining robust construction and thoughtful fitment.

Whether you are chasing peak horsepower numbers on a dyno or looking for a more responsive daily driver, the GrimmSpeed headers represent a carefully engineered upgrade. Before diving into material quality and installation, it helps to understand what makes these headers a standout choice for WRX owners who want both performance and longevity.

Material Quality: A Deep Dive

The material quality of any header directly impacts its performance, durability, and resistance to the extreme thermal cycles that exhaust components endure. GrimmSpeed uses 304 stainless steel throughout their headers, a material choice that balances corrosion resistance, heat tolerance, and structural integrity. This is not the same thin, low-grade stainless found in budget headers; GrimmSpeed specifies 14-gauge tubing, which provides substantial wall thickness without excessive weight.

Stainless Steel Construction and Its Advantages

304 stainless steel is a popular choice in high-performance exhaust systems because it resists rust and oxidation even under intense heat. For a part that lives close to the engine, this is critical. Stock Subaru exhaust manifolds are typically cast iron, which is heavy and prone to surface rust over time. Switching to a stainless steel header offers three distinct advantages:

  • Corrosion resistance: Stainless steel does not flake or rust like cast iron, meaning the header maintains its structural integrity for years, even in climates with road salt or high humidity.
  • Heat resistance: The 304 alloy can handle sustained temperatures well above 1,400 degrees Fahrenheit without warping or cracking. This is especially important for turbocharged applications where exhaust gas temperatures can spike during aggressive driving or tuning.
  • Weight savings: A full GrimmSpeed header setup weighs significantly less than the stock cast iron manifolds and crossover pipe. Reducing unsprung weight and overall vehicle mass contributes to better handling and acceleration.

Mandrel-Bent Tubing and Smooth Flow

GrimmSpeed uses mandrel-bent tubing, a process that preserves a consistent inner diameter through every bend. This is a non-negotiable feature for performance headers. When tubing is bent without a mandrel, the inner wall can collapse or crimp, creating restrictions that disrupt exhaust flow and increase back pressure. Mandrel bending ensures that the exhaust gases travel through the primaries with minimal turbulence, which directly supports faster turbo spool and higher peak horsepower.

The primary tubes on GrimmSpeed headers are carefully routed to equal lengths, which balances the exhaust pulses reaching the turbocharger. This design reduces the risk of reversion (where exhaust pressure pulses interfere with each other) and allows the tuner to extract more power safely. The collector is also smoothly merged, further minimizing flow disruption.

Welding and Fitment Quality

Another area where GrimmSpeed excels is in the quality of their TIG welding. Each joint is cleanly welded with consistent bead appearance, indicating good penetration and strength. Poor welds can lead to cracks over time, especially in a part that expands and contracts with every heat cycle. GrimmSpeed backs their headers with a limited lifetime warranty, which reflects their confidence in the fabrication quality.

Fitment is a common concern with aftermarket headers, as engine bay tolerances are tight on the WRX. GrimmSpeed designs their headers to bolt on without requiring modification to the engine crossmember or oil pan. They also include all necessary hardware, gaskets, and studs, which simplifies the installation process and ensures that everything lines up correctly the first time.

Performance Benefits: What You Can Expect

Installing GrimmSpeed headers is not just about weight savings or material quality; the real payoff is in how the car performs. Because the headers are designed as equal-length units, they optimize the exhaust pulses entering the turbocharger. This has several measurable effects on engine output and drivability.

Horsepower and Torque Gains

Most WRX owners who pair GrimmSpeed headers with a proper tune see gains in the range of 15 to 25 wheel horsepower and similar increases in torque. The gains come from reduced back pressure and more efficient turbo spool. The header allows the turbo to reach its target boost pressure sooner, which shifts the torque curve to the left and makes the car feel noticeably punchier in everyday driving.

It is important to note that these headers are designed to be used with a tune. Running a header without recalibrating the engine management system can lead to boost creep or lean conditions, which can damage the engine. GrimmSpeed recommends a professional tune to take full advantage of the flow improvements and to ensure safe air-fuel ratios.

Turbo Spool and Response

One of the most noticeable changes after installing GrimmSpeed headers is how quickly the turbo spools. On a stock WRX, there is often a slight lag before boost builds, especially at lower RPM. The equal-length design improves exhaust pulse energy, helping the turbo spin up faster. This means boost comes on earlier and more predictably, which is especially beneficial for autocross, track driving, or any situation where immediate throttle response matters.

Exhaust Sound Characteristics

Switching from the stock unequal-length header to an equal-length setup does change the exhaust note. The iconic Subaru boxer rumble, characterized by a distinct off-beat cadence, is largely a product of the uneven firing pulses traveling through unequal-length primaries. Equal-length headers smooth out those pulses, producing a more even, higher-pitched exhaust tone similar to a high-performance four-cylinder race car. Some enthusiasts prefer this sound for its aggressive, rev-happy character, while others miss the traditional rumble. If maintaining the classic Subaru sound is a priority, this is something to consider before purchasing.

Installation Guide: Tips for a Successful Swap

Installing headers on a WRX is an intermediate-level job that requires patience, the right tools, and attention to detail. The process typically takes four to six hours for someone with basic mechanical experience. Below is a step-by-step breakdown that covers preparation, common pitfalls, and best practices.

Tools and Parts You Will Need

Before starting, gather everything you will need. Running to the store mid-installation is frustrating and wastes time.

  • Socket set with extensions (10mm, 12mm, 14mm, 17mm)
  • Combination wrenches
  • Torque wrench (capable of reading in inch-pounds and foot-pounds)
  • Breaker bar or impact gun
  • Penetrating oil (such as PB Blaster or Kroil)
  • New exhaust gaskets (cylinder head gaskets and turbo inlet gasket)
  • Anti-seize compound for studs and bolts
  • Jack and jack stands or a lift
  • Eye protection and gloves

Preparation and Safety

Work on a cool engine. Exhaust components retain heat for a long time after the engine is shut off, and attempting to remove hot bolts increases the risk of stripping threads or burning yourself. Disconnect the negative battery terminal to prevent any electrical issues while working near sensors. If the car has an aftermarket downpipe or turbo heat shield, those may also need to be removed for access.

Step-by-Step Installation Process

The removal process starts from the bottom of the car. Raise the vehicle securely on jack stands and give yourself enough clearance to work comfortably. Remove the factory heat shields from the stock exhaust manifolds and crossover pipe. These shields are often held on by small bolts that can be rusted; penetrating oil helps here.

Unbolt the downpipe from the turbo to create slack in the exhaust system. This makes it easier to maneuver the stock manifold out. The header bolts are accessible from underneath and from the top of the engine bay. Use a long extension and a swivel socket for the rear cylinder head bolts, as they are the most difficult to reach.

Once the stock manifolds and crossover pipe are removed, clean the cylinder head mating surfaces. Any leftover gasket material or debris can cause exhaust leaks. Apply a thin coat of anti-seize to the new studs provided by GrimmSpeed before threading them into the cylinder heads. This prevents galling and makes future removal easier.

Install the new header gaskets onto the studs, then position the GrimmSpeed headers. It is common for both sides to need slight wiggling to line up with the studs simultaneously. Do not fully tighten any bolts until all pieces are in place. Start all nuts by hand to avoid cross-threading. Once everything is loosely assembled, tighten the header nuts in a crisscross pattern to the manufacturer's specifications.

Torque Specifications and Final Checks

GrimmSpeed provides specific torque values in their instruction manual. Typically, the header-to-head nuts are tightened to 26-30 ft-lbs, and the crossover pipe connections to a similar value. Using a torque wrench is essential because overtightening can strip the studs or warp the flanges, while undertightening leads to exhaust leaks. After torqueing everything, reinstall the downpipe and any heat shields that still fit. Some aftermarket headers may require trimming or removal of the stock heat shields; GrimmSpeed headers are designed to clear most factory shields, but always check clearance before finalizing the install.

Start the engine and listen for any exhaust ticks or leaks. A small leak often sounds like a tapping or puffing noise that increases with RPM. If you detect a leak, allow the system to cool and re-torque the affected bolts. It is normal for new gaskets to settle after a few heat cycles, so re-torquing after 100-200 miles is a good practice.

Maintenance and Longevity

Once installed, GrimmSpeed headers require relatively little maintenance. The stainless steel construction resists corrosion, but it is still a good idea to inspect the welds and flanges periodically, especially if the car is driven in harsh conditions or sees frequent track use. Over time, the natural blueing or discoloration of the stainless steel is normal and does not affect performance.

If you ever need to remove the headers for engine work, the anti-seize applied during installation will make the job significantly easier. Replacing the gaskets at that time is recommended to prevent leaks. With proper installation and reasonable maintenance, a set of GrimmSpeed headers should outlast the life of the engine.

Comparison to Other Header Options

The WRX aftermarket offers several header choices, including offerings from Tomei, Killer B Motorsport, and Invidia. Compared to these competitors, GrimmSpeed headers stand out for their combination of warranty support, fitment precision, and moderate pricing. Tomei headers are lighter but often louder due to thinner wall tubing, while Killer B headers are known for their extreme durability and smooth transitions but come at a higher price point. Invidia offers a budget-friendly option, but some users report fitment issues on certain chassis years.

GrimmSpeed strikes a balance that appeals to enthusiasts who want proven performance without the premium tax of boutique brands. Their lifetime warranty and comprehensive installation instructions add peace of mind that not all competitors offer.

Final Verdict

GrimmSpeed WRX headers are a well-engineered upgrade that delivers real performance benefits, durable construction, and thoughtful design details. The use of 304 stainless steel, mandrel-bent tubing, and high-quality TIG welding positions them among the best aftermarket header options for the Subaru WRX. Installation is achievable for a motivated DIYer with basic mechanical skills, and the gains in horsepower, torque, and turbo response are substantial when paired with a proper tune.

Whether you are building a track-focused WRX or simply want to unlock more potential from your daily driver, the GrimmSpeed headers offer a compelling return on investment. The only trade-off is the change in exhaust note, which is worth evaluating if the classic boxer rumble is an essential part of your Subaru experience. For everyone else, this is a header that performs as well as it looks and keeps delivering for years of hard driving.

For more details on installation or to find the correct part number for your specific WRX model year, visit the official GrimmSpeed website or consult trusted Subaru forums like NASIOC for community feedback.