The Ultimate High Performance FA24 Long Block Guide

You’ve added the bolt-on parts and done the initial tunes, but now you’re ready for the next level of power. The desire for more performance inevitably leads you to the heart of the car: the engine itself. To support a larger turbo and more aggressive tuning, you need an engine core that won't fail under pressure. A high performance FA24 long block provides the necessary strength, featuring a closed-deck design and forged internals built to withstand extreme cylinder pressures. This article explains the technical differences between a stock and built motor, what performance gains are realistic, and how to select an engine that matches your power goals and ensures long-term reliability.

Key Takeaways

• A Built Block Is the Foundation for Serious Power: A high-performance FA24 long block is specifically engineered with reinforced components, such as forged internals and a closed deck, to handle intense cylinder pressures. This makes it the necessary foundation for safely exceeding factory power levels with aggressive tuning.
• A Long Block Needs Supporting Mods: The engine is just one piece of the puzzle; to get the most out of your investment, you must upgrade your fuel system, turbo, and exhaust. A professional ECU tune is non-negotiable for integrating these parts and ensuring your engine runs safely and performs optimally.
• Protect Your Investment with a Great Builder and Proper Care: An engine's longevity depends on the builder's craftsmanship and your own maintenance habits. Select a builder with a proven reputation and a strong warranty, then commit to a diligent maintenance schedule with frequent oil changes to ensure reliable performance for years.

What Is a High-Performance FA24 Long Block?

If you're looking to get serious power out of your Subaru, you've likely heard the term "long block." A high-performance FA24 long block is a fully assembled engine core, from the oil pan to the cylinder heads, that has been re-engineered for one purpose: to handle significantly more power and stress than a factory engine. Think of it as the heart of your performance build, meticulously crafted with superior components to deliver the durability and output that enthusiasts demand.

These engines are the foundation for anyone wanting to push their Subaru WRX or other FA24-equipped model far beyond its stock limits. Instead of just replacing parts, a high-performance long block is a complete, integrated system designed for maximum strength and efficiency, allowing you to run higher boost and make more power without sacrificing reliability.

How It Differs From a Stock Engine

While the stock FA24 engine is a capable starting point, a high-performance long block is in a different league. The primary difference lies in the quality and strength of the internal components. A stock engine is built to meet a balance of performance, cost, and mass-production efficiency. A high-performance long block, on the other hand, is built with a singular focus on strength.

This involves upgrading critical components to handle increased cylinder pressure and heat. Modifications are made to improve airflow, manage thermal stress more effectively, and reinforce the block itself. This allows the engine to safely support the higher boost levels from larger turbos and aggressive engine tuning, turning your car into a true performance machine.

FA24 vs. FA20: What’s the Difference?

The FA24 engine represents a major step forward from its 2.0-liter predecessor, the FA20. The most significant difference is the increased displacement; the FA24 is a 2.4-liter engine. This larger size naturally produces more torque across the entire power band, giving you a more responsive and powerful driving experience even before major modifications.

This larger displacement also provides a stronger foundation for building power. The FA24’s design incorporates lessons learned from the FA20, resulting in a more robust block and improved engineering from the factory. For builders, this means the FA24 has a higher power potential, making it the preferred platform for modern Subaru performance parts and high-horsepower projects.

The Role of Closed Decks and Forged Internals

Two terms you'll frequently encounter with high-performance long blocks are "closed deck" and "forged internals." A closed-deck conversion is a modification that reinforces the top of the cylinder block. This adds structural integrity and prevents the cylinder walls from flexing or distorting under the extreme pressure of high boost, which is a common failure point in highly stressed engines.

Forged internals refer to components like pistons and connecting rods that are manufactured using a forging process, making them incredibly dense and strong. Unlike the cast parts found in a stock engine, forged components can withstand immense heat and pressure. Combining a closed deck with forged internals creates an engine block that is prepared for the demands of the track, trail, or any high-performance application you have in mind.

What Performance Gains Should You Expect?

Swapping to a high-performance FA24 long block is about building a reliable foundation for serious power. While the final numbers on the dyno depend heavily on your supporting modifications and tune, a well-built engine completely changes what your Subaru is capable of. It’s not just about hitting a peak horsepower number; it’s about achieving usable power across the entire rev range and doing it safely, run after run. Let's look at what you can realistically expect when you upgrade and what factors play into those impressive figures.

Real-World Horsepower and Torque Gains

With a quality FA24 long block and the right supporting parts, the performance increase is substantial. Even before a custom tune, you can see gains of around 50 horsepower and 70 lb-ft of torque at the wheels. However, the real magic happens after professional engine tuning services. With a proper tune, it’s possible to find an additional 70 horsepower and 100 lb-ft of torque. This brings the total potential gains to over 120 horsepower and 170 lb-ft of torque compared to your stock engine. These numbers transform your car’s acceleration and driving dynamics, providing the thrilling performance you’re looking for.

Understanding Tuning Potential and Power Limits

The stock FA24 is a capable engine, but it has its breaking point. In the tuning community, it’s been shown that a stock FA24 engine can fail when pushed to around 645 horsepower and 540 lb-ft of torque. This is precisely why a built long block is so critical for anyone serious about making big power. A high-performance long block with forged internals is engineered to handle the increased stress from higher cylinder pressures and more aggressive tuning. It allows you to safely push past the stock engine’s limits and build a reliable setup that won’t leave you stranded.

Common Myths About FA24 Performance and Reliability

One of the biggest truths about the FA24 is that it’s a significant improvement over the older FA20 engine, offering much greater power potential right out of the box. However, a common myth is that the stock internals are sufficient for major power goals. Many enthusiasts wish Subaru would include forged internals from the factory, but the reality is that stock components are designed for stock power levels. Forging a path to higher horsepower requires stronger performance parts. A built FA24 long block isn't just an upgrade; it's the correct way to achieve your performance ambitions without compromising your engine's longevity.

How to Choose an FA24 Long Block Builder

Selecting the right builder for your FA24 long block is one of the most critical decisions you’ll make for your Subaru. This isn't just about buying a part; it's about commissioning the new heart of your vehicle. The builder you choose determines the engine's ultimate power, reliability, and longevity. A great builder combines precision engineering with high-quality components and backs their work with a solid warranty and a stellar reputation. Making the right choice means you get a powerhouse engine you can trust on the track or trail. Let's walk through the key things to look for to ensure you partner with a builder who will deliver on their promises and give your Subaru the performance foundation it deserves.

The Crawford Performance Standard

When you're vetting an engine builder, their internal standards for quality and assembly should be your top priority. A premier builder doesn’t just assemble parts; they follow a meticulous process of machining, balancing, and blueprinting every component to exacting specifications. At Crawford, every engine is built with the highest quality performance parts and assembled by expert technicians who live and breathe Subarus. This commitment to precision ensures every engine that leaves our shop is reliable and ready to perform. Look for a builder who is transparent about their process and can prove their dedication to quality, as this is the foundation of a powerful and durable engine.

What to Look for in a Warranty

A warranty is more than just a safety net; it’s a direct reflection of the builder's confidence in their product. A vague or limited warranty can be a red flag, so it's important to read the fine print. A strong warranty should clearly outline what is covered, for how long, and under what conditions. For example, we stand behind our work with a 12-month/12,000-mile warranty on our engines, giving you peace of mind and a clear guarantee of our craftsmanship. When comparing builders, ask about their warranty policies and whether they cover both parts and labor. This single detail can tell you a lot about the quality you can expect.

Evaluating a Builder's Reputation

In the performance world, reputation is everything. A builder's history is written in forum threads, customer reviews, and track day results. Before committing, do your homework. Spend time on Subaru forums like NASIOC, read testimonials, and see what the community is saying. A reputable builder will have a long track record of satisfied customers and a strong presence in the enthusiast community. They are often the ones sharing their knowledge, showcasing their custom builds, and standing by their work for years. Choosing a builder with a solid reputation is the best way to protect your investment and ensure a smooth, successful engine upgrade.

Key Factors for Comparing FA24 Long Blocks

Choosing the right FA24 long block is about more than just finding the highest horsepower number. A truly great engine is a balanced package of power, durability, and thoughtful engineering. When you're comparing options, you need to look at the complete picture. This means understanding what the performance ratings really mean, how long the engine is expected to last under stress, and whether it will actually fit your car and existing components without a major headache. Let’s break down the key factors you should always consider.

Interpreting Horsepower and Torque Ratings

Horsepower and torque figures are exciting, but they are only part of the story. An FA24 long block has incredible potential; a standard tune can easily add 50 horsepower and 70 lb-ft of torque at the wheels. With the right supporting mods and more aggressive engine tuning services, some builders see gains of over 100 horsepower. However, the most important question isn't how much power it can make, but how reliably it delivers that power. A well-built engine will produce strong, consistent numbers across the entire power band without sacrificing stability. Always look for dyno charts that show a smooth, usable power curve, not just a flashy peak number.

Assessing Durability and Longevity

Power is useless if the engine can't handle it. The durability of an FA24 long block depends entirely on its build quality and how you use it. We've seen tuners push these motors to their absolute limits, with failures happening around the 645 horsepower mark. Other builds have successfully run at 600 wheel horsepower for over 30,000 miles before needing a refresh. This tells us that while the FA24 is strong, it has its limits. When choosing a long block, consider your goals. Are you building a weekend track car or a powerful daily driver? A reputable builder uses high-quality performance parts and assembly techniques to ensure your engine can handle your power goals for years to come.

Ensuring Turbo Kit Compatibility and Fitment

Nothing stops a project faster than a part that doesn't fit. Before you commit to an FA24 long block, you must confirm its compatibility with your vehicle and turbo setup. Some long blocks are designed as direct, drop-in replacements for specific models, which can save you an enormous amount of time and fabrication costs during installation. For example, a properly prepared FA24 can be a straightforward swap for a Subaru WRX or BRZ. Always verify fitment with the engine builder and cross-reference the requirements for your chosen turbo kit. This simple step ensures a smooth installation process and gets you back on the road, or track, much faster.

Judging the Quality of Internal Components

The heart of any high-performance engine is its internal components. The strength of an FA24 long block comes from the quality of the parts inside. A robust, closed-deck design provides superior cylinder wall strength, which is essential for handling the increased pressure from a turbocharger. Inside, you should look for premium components like forged Corilla connecting rods, custom JE pistons, and King performance race bearings. These parts are engineered to withstand extreme heat and pressure far better than stock components. An engine built with these high-quality internals is the foundation for making big power reliably, giving you confidence every time you turn the key.

What to Know Before You Buy an FA24 Long Block

Deciding to invest in a high-performance FA24 long block is a major step toward transforming your Subaru. Before you make the purchase, it’s important to understand the key factors that influence price, installation, and long-term performance. Thinking through these elements will help you set a realistic budget and ensure your build is a success from day one. A new engine is the heart of your car, and getting it right involves more than just the block itself.

What Determines the Final Price?

The price of an FA24 long block varies widely, and it all comes down to the build specifications. The final cost is directly tied to the engine's power handling capabilities. A long block engineered to handle 800 horsepower will naturally cost more than one rated for 600 horsepower because it requires stronger, forged internal components and more intensive labor to assemble. When you see different price points, you're typically looking at different tiers of durability and performance potential. Think of it as paying for peace of mind at higher power levels, ensuring your engine can handle the stress you intend to put on it.

Installation: Professional vs. DIY

While some long blocks are marketed as "drop-in" solutions, an engine swap is a complex job that demands precision. If you have extensive mechanical experience and a fully equipped garage, a DIY installation can be a rewarding project. However, for most enthusiasts, professional installation is the recommended path. An experienced technician ensures every component is installed correctly, all connections are secure, and the engine is prepared for its critical first start-up. This helps you avoid costly mistakes that could damage your new engine and ensures your vehicle’s engine tuning services are based on a solid mechanical foundation.

Essential Supporting Mods and ECU Tuning

A high-performance long block is just the starting point. To truly get the power and reliability you’re paying for, you need to invest in supporting modifications. Your stock fuel system, turbo, and exhaust were not designed to handle the output of a built engine. Upgrading these components is essential for performance and safety. Most importantly, a professional ECU tune is not optional. A custom tune from an expert calibrates your car’s computer to work with the new hardware, optimizing performance and ensuring the engine runs safely. Without a proper tune, you’re leaving significant power on the table and risking engine health.

Ongoing Maintenance for Your New Engine

Once your new FA24 is installed and tuned, your role in its longevity begins. A high-performance engine requires more diligent care than a stock motor. This means more frequent oil changes with high-quality synthetic oil, regular fluid checks, and paying close attention to how your car is running. The FA24 is a fantastic platform, but when you push it with performance parts, you must be proactive with maintenance. Consistent care is the best way to protect your investment and enjoy reliable power for years to come, whether you're on the track, the trail, or the street.

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Frequently Asked Questions

Do I really need a full long block, or can I just upgrade the parts in my current engine? While you can upgrade individual components in your stock engine, a professionally built long block provides a complete, blueprinted system. This means every part, from the pistons to the bearings, is selected and assembled to work in perfect harmony. This process removes the guesswork and risk of component mismatch, giving you a reliable foundation engineered from the ground up to handle specific power levels. It's the most dependable path to serious, lasting performance.

What is the break-in procedure for a new high-performance engine? A proper break-in is critical for the longevity of your new engine. The primary goal is to let the new piston rings seat correctly against the cylinder walls. This typically involves driving the car under varying engine speeds and loads, avoiding constant RPMs (like on the highway) and staying out of high boost for the first several hundred miles. An early oil change is also essential. Always follow the specific break-in instructions provided by your engine builder, as they will have the most precise guidelines for their build.

Will installing a built long block affect my car's factory warranty? Yes, you should expect that installing a high-performance long block will void your vehicle manufacturer's powertrain warranty. Factory warranties are designed to cover stock components operating under normal conditions. When you significantly increase an engine's power output with aftermarket parts, you are operating outside of those factory parameters. This is a standard trade-off that enthusiasts make when choosing to build their car for a higher level of performance.

Besides the engine, what other parts are essential to upgrade at the same time? A built engine is only as strong as its supporting systems. To safely achieve your power goals, you must upgrade several other key components. A robust fuel system, including a higher-flow fuel pump and injectors, is non-negotiable to prevent leaning out the engine. You will also need a professional ECU tune to calibrate everything to work together. Depending on your power target, a larger turbocharger, an upgraded clutch, and enhanced cooling systems for oil and coolant are also necessary investments.

How does a built FA24 long block affect daily driving? A properly built and tuned FA24 can make for an excellent daily driver, often feeling even better than stock. The increased displacement of the FA24 provides a significant boost in low-end torque, which makes the car feel more responsive and powerful in normal city driving, even when you aren't pushing it hard. The key is a quality tune that balances immense power potential with smooth, predictable behavior for your everyday commute.