Built EJ25 Long Block: A Complete Buying Guide

If you’re a Subaru owner, you’ve likely heard the horror stories about ringland failure or the limits of the stock motor. Pushing for more power with a bigger turbo or an aggressive tune can feel like a gamble. This is where upgrading to a built EJ25 long block becomes less of a modification and more of an insurance policy for your vehicle. It replaces the vulnerable factory internals with high-strength, forged components designed to handle serious stress. This guide is for anyone tired of worrying about their engine's limits. We'll cover what defines a quality build, how to choose the right components for your power goals, and what it really costs to create a reliable powerhouse.

Key Takeaways

• Build for Reliability First: A built long block swaps weak factory internals for durable forged components. This creates a strong foundation that protects your engine from failure when you add more power through tuning and other upgrades.
• Match Components to Your Goals: Your build is a complete system, not just an engine. Define your target horsepower first, then select a balanced combination of internals, fuel system upgrades, and cooling components that work together to achieve your goal safely.
• Account for the Total Project Cost: The price of the long block is just one part of the equation. A realistic budget must also include professional installation, a custom tune, and essential supporting parts like a fuel pump and radiator to ensure your investment is protected.

What is a Built EJ25 Long Block?

A built EJ25 long block is a fully assembled engine designed for Subaru owners who want to push past the limits of the stock motor. Think of it less as a replacement part and more as a foundational upgrade for serious performance. When you start adding a bigger turbo, aggressive tuning, and other modifications to your Subaru WRX or STI, the factory engine components become the weakest link. A built long block solves this problem by replacing those vulnerable parts with high-strength, forged internals.

This comprehensive assembly includes the engine block, crankshaft, connecting rods, and pistons (the "short block"), plus the cylinder heads, camshafts, and valvetrain. This isn't just about chasing massive horsepower numbers; it's about building a durable, reliable powerhouse. A professionally built long block is engineered to handle the increased stress of high-performance driving, whether you're on the track or a winding back road. It’s a complete solution that provides peace of mind, knowing your engine has been assembled with precision-matched components designed to work together flawlessly. Essentially, investing in a built long block is like buying an insurance policy against catastrophic engine failure, creating a solid foundation for all your future power goals.

Stock vs. Built: What's the Difference?

The main difference between a stock and a built EJ25 comes down to the strength of the internal components. Your factory Subaru engine is built with cast pistons and connecting rods, which are perfectly adequate for daily driving and stock power levels. However, when you increase boost and horsepower, these parts can fail under the added pressure. A built engine swaps these stock parts for high-strength, forged internals. Forged components are created under extreme pressure, making them denser and far more durable. This allows a built engine to reliably handle significantly more power and abuse than its stock counterpart, forming the core of any serious performance parts upgrade.

The Benefits: More Power and Reliability

The primary benefits of upgrading to a built EJ25 long block are simple: more power and greater reliability. With a reinforced foundation, you can safely push your engine to power levels that would destroy a stock block. Many built long blocks are designed to handle well over 500 horsepower, giving you the confidence to install a larger turbo and get an aggressive tune without worrying about internal failure. This upgrade transforms your vehicle's potential. Beyond raw power, you gain immense reliability. A built engine is engineered for durability under stress, making it ideal for track days, autocross, or even spirited daily driving. It’s an investment in your car’s longevity and your own peace of mind.

Long Block vs. Short Block: Which Do You Need?

Choosing between a long block and a short block depends on your budget, timeline, and mechanical skill. A short block consists of the engine block, crankshaft, pistons, and connecting rods—the bottom end. A long block includes the entire short block plus the cylinder heads, camshafts, and valvetrain. It's essentially a complete engine, ready for your intake, exhaust, and accessories to be bolted on.

If you have the expertise and time to assemble the top half of the engine yourself, or if you want to use custom cylinder heads, a short block can be a good option. However, a long block is a more integrated, plug-and-play solution. It eliminates the guesswork of matching heads to the block and ensures all critical components are assembled by professionals in a clean environment. For most Subaru STI owners seeking a reliable, straightforward installation, the long block is the superior choice.

Who Makes the Best Built EJ25 Long Blocks?

When you’re ready to invest in a built EJ25 long block, you’ll find several reputable builders in the Subaru community. Each has a unique approach to engineering, component selection, and assembly. The right choice for you will depend on your power goals, budget, and how you plan to use your car—whether it's for daily driving, track days, or off-road adventures. Choosing a builder with a proven track record is the most important step in ensuring your engine delivers both the performance you crave and the reliability you need. Let's look at some of the top names in the industry.

Crawford Performance

At Crawford Performance, we see a built engine as more than just a collection of high-performance parts; it’s an insurance policy against catastrophic failure. Our philosophy centers on creating a durable foundation that can safely handle the stress of significantly higher horsepower and aggressive tuning. By upgrading to forged internals, we build EJ25 long blocks designed for longevity and resilience. Every engine we assemble is backed by our unique 12-month/12,000-mile warranty, giving you peace of mind on the street and the track. Our engine tuning services are tailored to get the most out of your new build, ensuring every component works in perfect harmony.

IAG Performance

IAG Performance is a well-known name in the Subaru world, offering a wide variety of long blocks for models like the WRX, STI, Legacy GT, and Forester XT, covering years from 2002 to the present. They provide different engine stages designed to meet specific performance targets, from street-friendly builds to all-out race applications. Their extensive catalog gives drivers plenty of options to find an assembly that matches their horsepower goals. IAG’s long blocks are a popular choice for those looking for a comprehensive engine solution from a single, established source.

GCH Longblock Racing

GCH Longblock Racing specializes in high-performance engine packages built for serious power. They are known for options like their EJ255 Stage 1 Long Block, which is rated for up to 625 BHP with specific rod upgrades. GCH prides itself on building its engines in-house and performing thorough quality checks to ensure each unit meets their high standards. For drivers aiming for big horsepower numbers and a build focused purely on performance, GCH offers packages engineered to withstand extreme conditions. Their engine packages are a testament to their commitment to pushing the limits of the EJ25 platform.

Flatirons Tuning

Flatirons Tuning is a respected supplier that offers complete, valve-cover-to-valve-cover crate engines, making them a great resource for enthusiasts looking for a "drop-in" solution. They prominently feature IAG's long block packages, such as the IAG 550, which balances strong performance with dependable reliability. By providing fully assembled engines, Flatirons Tuning simplifies the upgrade process for many Subaru owners. Their IAG 550 Long Block is a popular option for those who want a straightforward path to a more powerful and reliable EJ25 without sourcing parts individually.

Define Your Power Goals and Key Components

Building an EJ25 long block isn't a one-size-fits-all project. The right combination of parts depends entirely on what you want to achieve with your Subaru. Before you even think about adding parts to a cart, you need a clear vision for your build. Are you aiming for a reliable daily driver with a bit more punch, a weekend track weapon, or a torque-heavy overlanding rig? Answering this question first will guide every other decision you make, ensuring you invest in a setup that’s perfectly matched to your goals and driving style. This section will walk you through the key components and considerations that form the foundation of any successful engine build.

Choosing Your Target Horsepower and Torque

Your target horsepower and torque numbers are the blueprint for your entire engine build. This single decision influences which block you choose, the type of internals you need, and what supporting modifications will be required for your fuel system, turbo, and transmission. A goal of 400 horsepower has a very different parts list—and price tag—than a goal of 700 horsepower. Be realistic about your budget and how you plan to use the car. A higher power target demands stronger, more expensive components and often requires more frequent maintenance. The performance parts you select should create a balanced system that can reliably deliver the power you’re aiming for without creating weak points elsewhere.

Essential Upgrades: Forged Internals and Cylinder Heads

The factory cast pistons and connecting rods in an EJ25 are not designed to handle significant power increases. This is where forged internals come in. Upgrading to forged pistons and rods is the single most important step in building a durable engine. Think of a built short block as an insurance policy against catastrophic failure; it creates a robust foundation that can safely handle the stress of higher boost and aggressive tuning. To complement this strong bottom end, consider your cylinder heads. Ported and polished heads improve airflow in and out of the engine, allowing it to breathe more efficiently and make more power without extra strain. This combination ensures your engine is strong from the inside out.

Open-Deck vs. Closed-Deck: Which is Right for You?

The design of your engine block is critical for cylinder wall stability, especially under high boost. Stock EJ25 blocks are "open-deck," meaning the coolant passages are open around the tops of the cylinders. This is fine for stock power levels, but the cylinders can flex or distort under high pressure. For serious power goals (typically 500+ hp), a "closed-deck" block is the superior choice. This design adds structural reinforcement to support the cylinder walls, preventing movement and ensuring better piston ring seal. This results in increased power output, extended engine life, and the ability to rev higher, making it the ideal foundation for a track or race build.

Aligning Your Build with Your Driving Style

The best engine build is one that’s perfectly aligned with how you drive. A setup designed for drag racing, with a massive turbo and aggressive cams, will feel sluggish and frustrating in daily city traffic. Conversely, a build focused on low-end torque for off-roading won’t have the high-RPM power needed for a road course. Think about where you want your powerband to be. Do you need instant response for autocross or sustained power for long track sessions? Every component, from the turbo size to the camshaft profile, should serve your primary goal. Working with a professional on your engine tuning services is the final step to ensure all your chosen components work together harmoniously.

How Much Does a Built EJ25 Long Block Cost?

Investing in a built EJ25 long block is a serious commitment, and the final price tag can vary widely. The cost isn't just for the engine itself; it’s a comprehensive package that includes the builder's expertise, the quality of the components, and the power level you're aiming for. A base-level performance long block might start around $8,000, while a high-horsepower, track-ready build can easily exceed $15,000 or more.

Think of the cost in three main parts: the engine, the supporting modifications, and the labor. The long block is the heart of your build, but it can't perform reliably without the right fuel system, cooling upgrades, and a professional tune. When you start shopping, you'll see prices from various builders, each with different philosophies and component choices. It’s crucial to look beyond the initial number and understand what’s included in the package, what isn't, and what you'll need to budget for separately to complete the project correctly. This ensures you're not just buying an engine, but a reliable performance solution that matches your goals.

Breaking Down the Price by Brand and Power Level

The price of a built long block is directly tied to its power-handling capabilities. For example, a builder might offer a 550-horsepower-rated long block for around $10,000, while their 750-horsepower version with a closed-deck block and upgraded internals could be closer to $13,000. This price difference reflects the stronger, more expensive components required to handle the additional stress. Brands like Crawford Performance engineer their blocks with specific parts and clearances designed for proven reliability at different power levels. When comparing prices, look at the details: are the cylinder heads ported? What brand of forged pistons and rods are used? The answers to these questions justify the cost and help you choose an engine that aligns with your performance targets and budget.

Factoring in Installation and Supporting Mods

The price of the long block is just the beginning. You also need to budget for installation and the essential supporting parts required to make it run properly. Professional installation can cost several thousand dollars, depending on the shop's labor rates. Additionally, your new engine will need other performance parts to support its power output. This often includes an upgraded fuel pump, injectors, a larger turbocharger, a robust cooling system, and a new clutch that can handle the increased torque. Some companies offer installation kits with necessary gaskets and fluids, but these rarely include the critical performance upgrades. Forgetting to budget for these items can bring your project to a halt.

Avoiding Common Budgeting Mistakes

A frequent mistake is focusing solely on the engine's power rating while neglecting the components that ensure its reliability. There's a common misconception that a block rated for high horsepower is automatically durable. In reality, its longevity depends entirely on the quality of the tune, the consistency of the fuel delivery, and the efficiency of the cooling system. Skimping on a professional engine tune or using a stock fuel pump is a recipe for disaster. Also, remember to account for "while-you're-in-there" jobs. Replacing a worn clutch or aging engine mounts is much cheaper and easier while the engine is out of the car.

Investing in Long-Term Reliability

Viewing a built EJ25 long block as an investment rather than just a purchase is key. A professionally assembled engine from a reputable builder is an insurance policy against the catastrophic failures that can plague modified stock engines. You're paying for precision machining, expert assembly, and high-quality components that are designed to work together seamlessly. Builders who stand behind their work, like Crawford Performance, often provide a warranty—our 12-month/12,000-mile warranty offers peace of mind that you're getting a reliable product. Ultimately, spending more upfront for a well-engineered long block saves you money and headaches down the road, letting you enjoy the power without the worry.

Don't Forget These Supporting Systems

Dropping a built EJ25 long block into your Subaru is a major step toward achieving your performance goals, but the engine itself is only part of the equation. To truly get the power, reliability, and longevity you’re paying for, you need to address the systems that support it. Think of it like building a house—a strong frame is essential, but it won't stand for long without a solid foundation, proper plumbing, and a functional electrical system.

For your engine, these supporting systems include fuel delivery, cooling, and engine management. Pushing more power generates more heat and requires more fuel. If your stock components can't keep up, you risk starving the engine of fuel or letting it overheat, which can lead to catastrophic failure. This is where a holistic approach to your build becomes critical. Upgrading your long block without also upgrading these key systems is a recipe for disappointment and costly repairs. Before you finalize your budget, make sure you account for these essential performance parts that will protect your investment and help your new engine perform at its peak.

Upgrading Your Fuel and Cooling Systems

With a more powerful engine comes a greater demand for fuel and a lot more heat. Your stock fuel pump, injectors, and radiator were designed for factory horsepower levels, and they simply can't handle the needs of a built motor. To prevent fuel starvation under load, you’ll need to install a higher-flow fuel pump and larger injectors. This ensures your engine receives the precise amount of fuel it needs to make power safely.

On the cooling side, an upgraded aluminum radiator and an external oil cooler are crucial for managing the increased temperatures. A built EJ25 running hot is an engine at risk. These Subaru WRX upgrades are not optional—they are essential insurance for keeping your engine healthy, whether you're on the track or a backcountry trail.

The Importance of a Professional Tune

Installing a built long block without a professional tune is like buying a supercar and never taking it out of first gear. It’s also incredibly risky. Your Subaru’s Engine Control Unit (ECU) needs to be completely recalibrated to account for the new, high-performance components. A professional tuner will adjust critical parameters like air-fuel ratios, ignition timing, and boost pressure to create a custom map for your specific setup.

This process ensures your engine runs not only powerfully but also safely, preventing issues like detonation that can destroy a motor in seconds. Do not rely on an off-the-shelf map. Investing in expert engine tuning services is the single most important step you can take to protect your new engine and get the reliable performance you paid for.

Your Guide to Engine Break-In and Maintenance

Your new built engine needs a proper break-in period to ensure all its components seat correctly for a long and healthy life. This isn't the time to see what it can do. For the first 1,000-1,500 miles, you’ll need to vary the engine RPM, avoid constant speeds, and stay out of high boost or high RPMs. This allows the piston rings to properly seal against the cylinder walls.

An early oil change after the first 500 miles is also critical to flush out any initial assembly lubricants and metal particles. After the break-in period, sticking to a strict maintenance schedule with high-quality fluids is key. A built engine is a significant investment, and consistent care is the best way to protect it for years to come.

Pro Installation vs. DIY: What to Consider

Deciding between a professional installation and a DIY project comes down to a realistic assessment of your skills, tools, and time. While tackling the job yourself can save money on labor, an engine installation is a complex and unforgiving task. A single mistake—a mis-torqued bolt or a forgotten connection—can lead to catastrophic failure and erase any initial savings.

A built long block is a major investment, and having it installed by a reputable shop provides peace of mind and often includes a warranty on the labor. For most owners, the expertise and security offered by a professional installer are well worth the cost, ensuring the job is done right the first time. This is especially true when you're working with high-end Subaru STI upgrades.

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Frequently Asked Questions

Is a warranty really necessary for a built engine? Absolutely. A warranty is the builder's vote of confidence in their own work. It shows they stand behind the quality of their components, machining, and assembly. A built engine is a major investment, and a warranty protects you from defects in materials or workmanship. It’s a clear sign that you're buying a professionally engineered product, not just a collection of parts, giving you peace of mind when you're pushing your car hard.

Why is the engine break-in period so strict? The break-in period is crucial for the long-term health of your new engine. During the first thousand miles or so, the piston rings need to seat perfectly against the cylinder walls to create a tight seal. This process, which requires varying engine speeds and avoiding high loads, ensures you get optimal compression and minimal oil consumption for the life of the engine. Rushing this step can lead to permanent performance issues, so patience here pays off significantly down the road.

How do I decide between a long block and a short block? The choice comes down to your timeline, technical skill, and desire for a complete solution. A short block is the engine's foundation, but you're responsible for sourcing and correctly installing the cylinder heads and valvetrain. A long block is a fully assembled unit from the oil pan to the valve covers. For most people, the long block is the better choice because it's assembled by professionals in a controlled environment, eliminating guesswork and ensuring all internal components are perfectly matched.

Can I still use my car as a daily driver with a built long block? Yes, you certainly can. A well-built engine with a professional tune can be just as reliable and easy to drive as a stock motor, just with a lot more power on tap. The key is to align the build with your driving style. If you communicate to your builder and tuner that daily driveability is a priority, they can select components like camshafts and a turbo that provide a smooth powerband without sacrificing reliability for everyday use.

My friend has a tune file for a similar setup. Can I just use that? Please don't. Every engine is slightly different, and factors like your specific turbo, fuel system, and even local climate can dramatically affect how it runs. Using a generic or "off-the-shelf" tune is one of the fastest ways to damage a new built engine. A professional tune is customized specifically for your car on a dynamometer, ensuring the air-fuel ratios and timing are perfect for your exact combination of parts. It's the most critical step in protecting your investment.