Subaru Cylinder Head Upgrades: A Complete Guide

Rebel vs Bandit vs Outlaw: Which Subaru Cylinder Head Upgrade?

Is your Subaru build hitting a wall? If your FA20 or EJ engine feels sluggish or you're just not getting the power you expect, the bottleneck is often the stock heads. A performance Subaru cylinder head is the gateway to more horsepower, sharper throttle response, and better stability at high RPM. At Crawford Performance, we engineered a three-tier lineup of Subaru cylinder heads—Rebel, Bandit, and Outlaw—so every driver can find the perfect fit for their build and finally get the power they're after.

Whether you’re chasing daily drivability, track-day dominance, or competition-level power, here’s how each option stacks up.

What Are Subaru Cylinder Heads and Why Upgrade?

Think of your Subaru's engine as a powerful air pump. The more air it can move in and out, the more power it can make. The cylinder heads are the gatekeepers of this process, sitting on top of the engine block and controlling the flow of air and fuel into the cylinders and the exhaust out. They house critical components like the valves, camshafts, and spark plugs, forming the roof of the combustion chamber where all the magic happens. Upgrading your cylinder heads is one of the most effective ways to improve your engine’s breathing ability, which is essential for making serious horsepower.

When you upgrade to a performance cylinder head, you're essentially opening up those gates wider. This is often done through a process called "porting and polishing," which smooths out and enlarges the intake and exhaust passages. This modification allows the engine to pull in more air and expel exhaust gases more efficiently. The result isn't just a higher peak horsepower number; it’s a complete change in your car's character. You’ll feel sharper throttle response, a stronger pull through the entire rev range, and greater engine stability when you’re pushing it hard on the track or trail.

The Role of Cylinder Heads in Engine Performance

The design of your cylinder heads directly dictates your engine's personality and performance ceiling. Every bit of air entering your engine and exhaust leaving it must pass through them. Factory heads are designed for a balance of performance, economy, and emissions, which often leaves room for improvement. Performance-oriented heads, like those we engineer at Crawford Performance, are optimized for maximum airflow. This allows for a more complete combustion cycle, which translates directly into more power. Better airflow means your engine doesn't have to work as hard to produce power, leading to improved efficiency and durability under high-stress conditions.

Signs of a Failing Cylinder Head

A failing cylinder head can cause some serious and often unmistakable problems with your engine. One of the most common signs is a significant loss of engine performance. If your Subaru feels sluggish, misfires, or struggles to accelerate, the issue could be rooted in the head. You might also notice your engine overheating frequently, even on short drives. This happens when a crack in the head allows coolant to leak into the combustion chamber or exhaust gases to enter the cooling system, disrupting its ability to regulate temperature. Keep an eye on your temperature gauge and address any sudden changes immediately.

Another tell-tale sign is visible smoke from the exhaust. If you see sweet-smelling white smoke, it’s a strong indicator that coolant is burning in the cylinders. Blue smoke typically points to oil leaking past the valve seals within the head and into the combustion chamber. You should also check your oil. If the oil on your dipstick looks milky or resembles a chocolate milkshake, it means coolant has mixed with it, often due to a cracked head or a failed head gasket. Any of these symptoms warrant an immediate and thorough inspection by a qualified technician to prevent catastrophic engine damage.

How to Diagnose a Bad Cylinder Head

Diagnosing a bad cylinder head requires a few key checks. Start with the simple visual inspections mentioned above: check for milky oil, white exhaust smoke, and persistent overheating. If you suspect a problem, a compression test is a great next step. This test measures the pressure in each cylinder, and a significant drop in one or more cylinders can point to a bad seal caused by a warped head, a blown head gasket, or damaged valves. A leak-down test can provide even more specific information by pressurizing each cylinder and identifying where the air is escaping—whether it's past the rings, intake valves, or exhaust valves.

Understanding Common Subaru Head Gasket Problems

In the Subaru world, especially with the EJ series engines, you can't talk about cylinder heads without mentioning head gaskets. The head gasket creates a critical seal between the cylinder head and the engine block. When it fails, it can cause the exact same symptoms as a cracked cylinder head: overheating, coolant and oil mixing, and loss of compression. In many cases, a severe overheating event caused by a failing head gasket can warp the cylinder head itself, meaning both components need to be addressed. That’s why any time you replace a head gasket, it’s crucial to have the cylinder heads professionally inspected and resurfaced to ensure a perfect seal.

Is It Worth Replacing Your Cylinder Head?

Deciding whether to replace your cylinder heads is a big step that depends entirely on your goals. If your current heads are damaged beyond repair from overheating or a mechanical failure, then replacement is a necessity. However, if you're planning a major power upgrade, replacing the heads becomes a strategic investment. Stock heads can become a bottleneck, limiting the gains from other modifications like a larger turbo or upgraded fuel system. A set of high-flowing performance heads ensures your entire engine package can work in harmony to produce reliable power.

For those building a dedicated track car or a high-horsepower street machine, a cylinder head upgrade is almost always worth it. It lays the foundation for all future performance gains. On the other hand, if you’re happy with simple bolt-on modifications and aren't chasing huge power figures, your factory heads may be sufficient. The key is to align the investment with your performance ambitions. If you're already tearing down the engine for a rebuild or a head gasket job, it's the perfect opportunity to upgrade and save on future labor costs.

Understanding Your Cylinder Head Options

Once you decide to upgrade, you'll find a wide range of options tailored to different goals and budgets. The choice isn't just about which brand to pick; it's about selecting a setup that matches your intended use, whether it's for a reliable daily driver, a weekend track toy, or an all-out race car. Understanding the difference between complete packages and bare heads, as well as the various performance tiers available, will help you make an informed decision that supports your build now and in the future.

Complete Packages vs. Bare Cylinder Heads

You can typically buy cylinder heads in two ways: as "bare" castings or as complete, pre-assembled packages. A bare head is just the metal casting, meaning you’ll need to source and install all the valvetrain components yourself—valves, springs, retainers, camshafts, and so on. This route offers maximum customization but requires significant expertise to ensure all parts are compatible and correctly installed. For most enthusiasts, a complete package is the better choice. These heads come professionally assembled with components that are carefully matched to achieve a specific performance goal, taking the guesswork out of the equation and ensuring reliability right out of the box.

Performance Tiers: From Street to Competition

Performance cylinder heads are often categorized into tiers, such as Street, Competition, and Race. A "Street" package is designed to improve power and response without sacrificing daily drivability, often featuring mild port work and upgraded valve springs. "Competition" heads are more aggressive, with extensive porting and high-performance valvetrain components built to handle higher RPM and boost levels, making them ideal for track days and serious street builds. "Race" or "Drag" tiers are the most extreme, optimized for maximum power in a specific RPM range, often at the expense of low-end torque and street manners.

Leading Brands for Subaru Cylinder Heads and Parts

The Subaru aftermarket is filled with talented shops and manufacturers. Companies like IAG Performance are well-known for their comprehensive engine programs and offer a variety of cylinder head options. At Crawford Performance, we've spent decades perfecting our craft on the track and the street, which led us to develop our own lineup of cylinder head packages. Our heads are engineered based on real-world racing experience and are built to deliver proven, reliable power for everything from daily-driven Crosstreks to competition-level STIs.

Essential Components for a Cylinder Head Replacement

Replacing your cylinder heads is more than just a simple swap. To do the job right and ensure your engine is reliable, you need to replace several supporting components at the same time. This is especially true for high-performance builds where every part of the system is placed under greater stress. Using old, worn-out gaskets or fasteners with new, high-performance heads is a recipe for failure. Planning for these essential components from the start will save you time, money, and headaches down the road, ensuring your new setup performs as expected.

Camshafts, Valves, and Springs

The valvetrain—camshafts, valves, and springs—is the heart of the cylinder head. Upgraded camshafts feature more aggressive profiles that hold the valves open longer, allowing more air to enter the engine for more power at higher RPMs. Larger valves physically increase the size of the doorway for air to flow through. Finally, stiffer valve springs are essential to prevent "valve float," a condition where the springs can't close the valves fast enough at high RPM, leading to a loss of power and potential engine damage. A well-matched set of these components is key to unlocking the full potential of your new heads.

Upgraded Gaskets for High-Power Builds

Never, ever reuse an old head gasket. When you're increasing cylinder pressures with more boost and power, the factory head gasket can quickly become a weak link. For any performance build, you should use a quality multi-layer steel (MLS) head gasket. These gaskets are designed to withstand the higher combustion pressures and temperatures of a modified engine, providing a much stronger and more reliable seal between the head and the block. This is a relatively small expense that provides critical insurance for your entire engine investment.

Budgeting for Your Upgrade: A Cost Breakdown

A cylinder head upgrade is a significant financial commitment, and it's important to go into it with a clear understanding of the total cost. The price of the heads themselves is just the starting point. You also need to account for all the necessary supporting parts, fluids, and the cost of professional labor if you aren't tackling the job yourself. Creating a detailed budget ahead of time will help you avoid surprises and ensure you can complete the project without cutting corners, which is crucial for the long-term health of your engine.

Standard vs. High-Performance Head Pricing

The cost of cylinder heads can vary dramatically based on the level of work performed. A pair of remanufactured stock heads might cost under a thousand dollars, while a set of fully ported, competition-ready heads with an upgraded valvetrain can easily exceed $5,000. The price difference reflects the extensive labor involved in CNC porting, the quality of the components used (like valves, springs, and retainers), and the level of professional assembly. Generally, you get what you pay for, and higher-priced heads offer a much greater potential for power and reliability in demanding applications.

The Cost of Supporting Parts and Labor

Beyond the heads themselves, you'll need to budget for a new head gasket set, head studs, timing belt or chain kit, water pump, thermostat, and fresh fluids like oil and coolant. These supporting parts can add several hundred to over a thousand dollars to the total bill. Labor is another major factor. A cylinder head replacement is a complex, time-consuming job. Depending on the shop's hourly rate, you can expect labor costs to be substantial. This is why it's often most cost-effective to perform this upgrade when the engine is already out for other work, like a short block replacement or head gasket service.

Engine and Model Compatibility Guide

Not all Subaru cylinder heads are created equal. With different engine series, valvetrain configurations, and subtle changes across model years, getting the right heads for your specific vehicle is absolutely critical. Installing incompatible heads can lead to poor performance, engine damage, or a car that simply won't run. Before you purchase anything, you must verify that the parts are designed for your engine type, model, and year. This ensures proper fitment and function, allowing you to get the performance you paid for without any compatibility nightmares.

Heads for FA20 and EJ Series Engines

Subaru's two most common modern performance engines are the EJ series (found in the STI and older WRX models) and the FA20/FA24 series (found in the newer WRX, BRZ, and Ascent). These engine families are fundamentally different in their design, and their cylinder heads are not interchangeable. The EJ engines have their timing belts, while the FA engines use timing chains. The port designs, combustion chambers, and mounting points are all unique. Always ensure you are buying heads specifically designed for your engine code, whether it's an EJ257, FA20DIT, or another variant.

SOHC vs. DOHC Configurations

You'll also see heads described as SOHC (Single Overhead Cam) or DOHC (Dual Overhead Cam). SOHC heads use a single camshaft per head to operate both the intake and exhaust valves, while DOHC heads use two separate camshafts for each function. DOHC designs allow for more precise valve control and better high-RPM breathing, which is why they are used in performance models like the WRX and STI. Most non-turbo models, like the Impreza and older Foresters, use SOHC heads. These two types are not interchangeable, so be sure to confirm which configuration your engine has.

Compatibility Across WRX, STI, Forester, and Other Models

Even within the same engine series, there can be variations between models and years. For example, while a Forester XT might share the same basic EJ25 engine as an STI, there can be differences in the heads related to emissions or supporting systems. It is essential to confirm part numbers and consult with experts to guarantee fitment. Whether you're upgrading a Forester for overlanding or building a track-focused WRX, verifying compatibility is the first step to a successful project. When in doubt, always check with the manufacturer or a trusted performance shop.

Crawford Performance Cylinder Head Packages

At Crawford Performance, we've poured decades of Subaru tuning and racing experience into developing a clear, three-tiered lineup of cylinder head packages designed to meet the needs of any build. We handle the complex work of matching components and precision assembly, so you can be confident you're getting a proven solution that's ready to perform. Each package is built to our exacting standards to deliver reliable power, whether you're looking for a responsive daily driver or a competitive race engine. Our goal is to provide a straightforward path to achieving your performance ambitions.

Our lineup includes the Rebel, Bandit, and Outlaw packages. The Rebel is our entry-level performance head, perfect for street cars and daily drivers looking for a significant improvement in power and throttle response without sacrificing reliability. The Bandit steps things up for the enthusiast who frequents the track or wants a seriously powerful street car, featuring more aggressive porting and a robust valvetrain. For those pushing the limits, the Outlaw is our top-tier competition head, engineered for maximum airflow and durability in the most demanding racing environments. No matter your goal, we have a cylinder head package to help you reach it.

Rebel Port Heads – Balanced Daily + Track Performance

The entry point into Crawford’s performance head lineup, Rebel Port heads are built for enthusiasts who want noticeable gains without sacrificing daily drivability. Precision porting improves airflow and throttle response, making them perfect for street/track crossover builds.

  • Best for: Daily-driven WRX, STI, BRZ/FR-S with bolt-ons or moderate turbo/supercharger setups.

  • Strengths: Balanced reliability, efficiency, crisp throttle response.

  • Ideal owner: The driver who rejects compromise, but still wants a car they can live with every day.

👉 Shop Rebel Port Heads

Bandit Breathers – Aggressive High-Output Builds

The middle tier, Bandit Breathers are tuned for bolder, more aggressive Subaru builds. With sharper response, higher RPM stability, and the ability to “steal” horsepower from every CFM of airflow, Bandit heads thrive in street/track crossover cars pushing serious power.

  • Best for: High-output WRX, STI, BRZ/FR-S with larger turbo or supercharger builds.

  • Strengths: Aggressive porting, high-RPM stability, extended race-duty durability.

  • Ideal owner: The enthusiast chasing every last horsepower without stepping fully into all-out race territory.

👉 Shop Bandit Breathers

Outlaw Heads – Maximum Race Performance

The top tier of Crawford’s cylinder head lineup, Outlaw heads are for those who want everything and more. With extreme porting, maximum airflow, and the durability to withstand sustained high-RPM abuse, these heads are built for competition-level Subaru FA20 and EJ builds.

  • Best for: WRX, STI, BRZ/FR-S running big turbos, high boost, and full race setups.

  • Strengths: Extreme airflow, max horsepower, race-winning reliability.

  • Ideal owner: The uncompromising driver who builds for the podium.

👉 Shop Outlaw Heads

Which Subaru Cylinder Head Is Right for You?

  • Choose Rebel if you want a balance of power and daily drivability.

  • Choose Bandit if you’re chasing aggressive performance with race-duty reliability.

  • Choose Outlaw if you’re building for max power, big boost, and competition-level racing.

No matter your choice, each set of Crawford Performance Subaru cylinder heads is engineered with precision porting, race-bred reliability, and decades of Subaru expertise.

👉 Explore the full lineup here: Crawford Cylinder Head Collection

Frequently Asked Questions

Do I have to upgrade my cylinder heads if I'm installing a bigger turbo? Think of it this way: a bigger turbo is like trying to force a tidal wave through a garden hose. Your stock heads can only flow so much air, and they will eventually become a bottleneck that chokes your engine's potential. To get the full benefit of a larger turbo and make reliable power, you need a set of performance heads that can handle the increased airflow.

My Subaru is overheating. Does that automatically mean I have a cracked cylinder head? Not necessarily, but it's a major red flag you shouldn't ignore. Overheating in Subarus, especially the EJ series, is often caused by a failing head gasket. However, a severe overheating event caused by a bad gasket can easily warp or crack the cylinder head itself. The two issues are very closely related, so a thorough inspection of both the gasket and the head surface is critical to finding the true cause.

What's the main difference in feel between the Rebel, Bandit, and Outlaw heads? The Rebel heads will make your car feel much more responsive and eager, like a sharper, stronger version of its stock self—perfect for a daily driver. The Bandit heads deliver a much more aggressive punch, especially in the mid-to-high RPM range, making the car feel like it wants to be pushed hard on a track. The Outlaw heads are all about maximum power; they create a raw, competition-focused experience where the engine truly comes alive at the highest RPMs.

If I'm already doing a head gasket job, should I just upgrade the heads then? Absolutely. The labor involved in a head gasket replacement is nearly identical to a full cylinder head swap, as the heads have to come off anyway. Upgrading while you're already in there is the most cost-effective way to do it. You'll save hundreds, if not thousands, in future labor costs and get a major performance improvement at the same time.

Will a cylinder head upgrade make my car unreliable for daily driving? Not at all, as long as you choose the right package for your goals. Our Rebel heads, for example, are specifically designed to improve power and throttle response while maintaining excellent street manners and reliability. The issues with drivability typically only appear with extreme, race-only setups that sacrifice low-end power for peak horsepower, which is what our Outlaw package is for.

Key Takeaways

  • Build Power on the Right Foundation: Stock cylinder heads are the primary bottleneck limiting your engine's airflow and horsepower potential. Upgrading them is the most effective way to help your engine breathe and support future power modifications.
  • Choose Heads That Match Your Goals: The best cylinder head is the one designed for your specific purpose. Align your choice with your build, whether it's a responsive daily driver, a high-output street car, or a dedicated competition vehicle, to get the performance you expect.
  • Plan for the Supporting Components: A cylinder head replacement is more than a simple swap. For a reliable and lasting build, always budget for essential supporting parts like performance head gaskets, upgraded head studs, and a refreshed valvetrain.

Related Articles

Back to blog