FA20 Short Block: Your Ultimate Buyer's Guide

You love your WRX or BRZ, but you’ve started to feel the limits of its factory power. You want more response, more acceleration, and the kind of performance that truly matches your car's potential. While bolt-on parts can get you part of the way there, serious horsepower goals require a stronger foundation. The stock internals can only handle so much before reliability becomes a concern. To build a truly powerful and durable engine, you need to start at its core. This is where a high-performance FA20 short block becomes the essential first step in your build.

Key Takeaways

• Match the block to your build: Choose an OEM short block for a simple, stock-power replacement. For higher horsepower, a built block with forged internals is necessary, but first confirm if your car has the naturally aspirated FA20D (BRZ/86) or the turbocharged FA20DIT (WRX).
• Plan for supporting modifications: A built short block is the foundation, not the entire build. To safely achieve more power, you must also upgrade supporting systems like your fuel pump, injectors, and oil cooler, followed by a professional tune.
• Prioritize the builder's expertise: Look for a builder with a proven history in motorsports, in-house engineering like closed-decking, and a strong warranty. A company's experience is critical for the long-term reliability of your high-performance engine.

What Is an FA20 Short Block?

If you're a Subaru enthusiast, you've likely heard the term "FA20 short block" tossed around in forums or at car meets. So, what is it exactly? Think of the short block as the heart of your engine. It’s the bottom-end assembly that includes the engine block, crankshaft, connecting rods, and pistons. For owners of the Subaru WRX or BRZ, upgrading to a high-performance short block is a common path to building a more powerful and reliable engine.

Choosing a short block is often the first step in a serious engine build. It’s perfect for those who want to replace a damaged engine core or create a custom setup from the ground up. Instead of buying a full engine, you get the foundational components, giving you the freedom to select the cylinder heads and other parts that match your specific power goals. Let's break down what that means for you and your build.

Short Block, Long Block, or Complete Engine?

When you're looking at engine options, you'll see three main choices: short block, long block, or a complete engine. Understanding the difference is key to getting exactly what you need. A short block is the base assembly, containing the block, crank, rods, and pistons. It’s the starting point for a custom build.

A long block takes it a step further. It includes everything in the short block plus the cylinder heads, camshafts, and valvetrain. This is a great option if you want a more assembled package but still plan to choose your own intake, turbo, and other accessories. A complete engine is just what it sounds like: a fully assembled, drop-in solution. Choosing the right one depends entirely on your project's scope, budget, and how hands-on you want to be.

What's in the Box (and What Isn't)

When you order an FA20 short block, it’s important to have clear expectations about what you’re receiving. A standard short block from most builders, including Subaru, will arrive as a pre-assembled bottom end. This means the crankshaft, connecting rods, and pistons are already installed in the engine block. You’ll get the core components that handle all the power and combustion.

What you won't find in the box are the cylinder heads, oil pan, timing components, or gaskets. This isn't an oversight; it's intentional. This approach gives you or your builder the flexibility to inspect, clean, and transfer your existing parts or purchase new performance parts to complete the engine. It’s your chance to customize the build to your exact specifications.

FA20D vs. FA20DIT: Know the Difference

Not all FA20 engines are created equal, and this is a crucial detail when buying a short block. The two main variants are the FA20D and the FA20DIT. The FA20D is the naturally aspirated engine found in the Subaru BRZ and Toyota 86. The FA20DIT, which stands for Direct Injection Turbo, is the power plant for the 2015 and newer Subaru WRX.

While they share a name, their internal components are designed for very different jobs. The FA20DIT features lower compression pistons built to handle turbo boost, while the FA20D has a higher compression ratio for responsive, non-turbo performance. Ordering the wrong short block will lead to major compatibility problems, so always confirm which engine your car has before making a purchase for your Subaru WRX upgrades.

Which Cars Have the FA20 Engine?

The FA20 is a versatile 2.0-liter flat-four boxer engine that has become a favorite in the enthusiast community. You'll find it under the hood of some of the most popular and mod-friendly cars from Subaru and Toyota. Because it was designed with performance in mind, it serves as an excellent platform for drivers looking to build a car that truly matches their ambitions, whether on the track or a winding back road. Understanding which models carry this engine is the first step in planning your performance journey.

FA20s in the Subaru and Toyota Lineups

The FA20 engine appears in a few key models, but the two most common are the Subaru WRX and the Subaru BRZ/Toyota 86 twins. The turbocharged FA20DIT variant powers the 2015 and newer Subaru WRX, a car with deep roots in rally and performance driving. This direct-injected turbo engine is known for its responsiveness and tuning potential right out of the box.

On the other side, you have the naturally aspirated FA20D, which is the heart of the first-generation Subaru BRZ and Toyota 86 (also sold as the Scion FR-S). These lightweight, rear-wheel-drive sports cars are praised for their exceptional handling and driver feedback, making them a pure joy to drive. The engine in these cars provides a solid, balanced foundation for a build.

Why WRX and BRZ Owners Upgrade Most

If you own a WRX or a BRZ, you already know these cars are built for fun. But you also know there’s more potential waiting to be unlocked. WRX owners often want to push past factory power levels, and the stock internals can only handle so much added pressure. For BRZ and 86 drivers, the chassis is brilliant, but many feel the engine could use more power to match the car's handling prowess.

This is why upgrading to a built short block is so common. A forged block provides the strength and reliability needed to handle significantly more power, whether you're adding a larger turbo to your WRX or a forced induction kit to your BRZ. It’s the fundamental step toward building a seriously fast and durable engine, which is why our engine tuning services are designed to maximize the potential of these powerful platforms.

Is Your FA20 Trying to Tell You Something?

That sinking feeling when you hear a new, unwelcome noise from your engine is something every enthusiast dreads. Whether it’s a subtle tick, a sudden loss of power, or the infamous knock, your FA20 is communicating with you. Ignoring these signals can lead to catastrophic failure, turning a manageable repair into a complete replacement. The key is to listen closely and diagnose the issue before it gets worse. Understanding the common failure points and knowing what to look for will help you make an informed decision about your engine's future.

Signs Your FA20 Is Failing

The first signs of trouble are often subtle. You might notice a slight hesitation during acceleration, an unusual amount of smoke from the exhaust, or a new sound that wasn’t there before. If you suspect something is wrong, one of the most important diagnostic steps is to have your cylinder heads inspected. Even if you plan on replacing the short block, your heads need to be in perfect condition to go on the new engine. A reputable machine shop can check them for warping, cracks, or valve guide issues that could compromise your new build. This proactive step can save you from putting a damaged head on a brand-new block.

Decoding Rod Knock and Oil Contamination

Rod knock is the most notorious FA20 failure. It’s a deep, rhythmic knocking sound that gets faster with engine RPM, and it’s a clear sign of a spun rod bearing. When a bearing fails, it sends tiny metal shavings throughout the entire engine via the oil system. This contamination is a serious problem. To confirm your suspicions, drain the engine oil and carefully cut open the oil filter. If you see metallic glitter in the oil or trapped in the filter media, you have definitive proof of internal damage. These metal particles can clog oil passages and damage other critical performance parts, turning a single component failure into a system-wide issue.

Should You Rebuild or Replace?

Once metal has circulated through your engine, a simple rebuild becomes much more complicated. Tiny metal fragments can get embedded in components with small oil passages, like cam adjusters, solenoids, and oil coolers. Even after a thorough cleaning, it’s nearly impossible to guarantee that all the debris has been removed. Reusing these contaminated parts on a new short block is a huge risk, as they can release particles that will destroy your new bearings. In these cases, it’s often safer and more cost-effective in the long run to replace these components and start fresh with a reliable short block, especially if you're looking for serious Subaru WRX upgrades.

OEM vs. Built FA20 Short Blocks: Which Is for You?

Choosing between an original equipment manufacturer (OEM) and a built short block is one of the most important decisions you'll make for your Subaru. The right answer depends entirely on your goals, your budget, and how much power you plan to make. One is a straightforward replacement, while the other is the foundation for a high-performance build. Let's break down which path is the right one for you and your car.

When to Stick with an OEM Block

An OEM short block is essentially a brand-new engine assembly straight from Subaru, containing the crankshaft, connecting rods, and pistons. If you're happy with your car's current performance and just need to replace a failed engine to get back on the road, the OEM route is a solid choice. It’s a direct, reliable replacement designed for factory power levels. For a daily driver with light modifications or a completely stock setup, sticking with an OEM block is the simplest and most cost-effective way to restore your vehicle to its original running condition without any extra fuss.

Why a Built Block Might Be Your Best Bet

If your plans involve more than just daily driving, a built block is the only way to go. As soon as you decide to add a larger turbo, run higher pressure, or push your car on the track, you exceed the limits of the stock components. A built short block is engineered from the ground up to handle immense stress. It features stronger, forged internal components that can withstand the intense heat and pressure of a high-horsepower engine. Think of it as the necessary foundation for any serious power build, ensuring your engine remains reliable as you add other performance parts.

Open Deck vs. Closed Deck: What It Means for Power

When you look at built blocks, you'll hear the terms "open deck" and "closed deck." The factory FA20 has an open-deck design, meaning there are gaps between the cylinder walls and the block for coolant to flow. This is fine for stock power, but under high pressure, the unsupported cylinder walls can flex or even crack. A closed-deck modification fixes this by adding material that braces the cylinder walls, making the entire structure significantly stronger. This process is a key part of a professional engine tuning service and is absolutely essential for anyone chasing 500 horsepower or more, as it provides the strength needed to handle extreme cylinder pressures reliably.

How Much Power Can an FA20 Handle?

This is one of the first questions every FA20 owner asks when they start thinking about modifications. You feel the potential in your WRX or BRZ and want to know just how far you can push it. The answer, as you might guess, isn't a single number. It depends entirely on the components inside your engine. A stock FA20 has its limits, but a properly built block can transform your Subaru into a completely different machine. The stock engine is designed for a great daily driving experience, balancing performance with longevity. But for those of us who want more, the aftermarket provides a clear path forward.

Understanding these limits is key to building a reliable, high-performance vehicle without risking catastrophic failure. It’s about making smart, informed decisions on your upgrade path. Pushing past the factory's intended power levels means you're taking on the role of the engineer, and that requires good information. We’ll look at the baseline power of a stock engine, see how forged internals change the game, and explore the real-world power figures you can expect from a built FA20. This knowledge will help you set realistic goals for your build and choose the right parts to get there safely, ensuring your investment pays off in thrilling, dependable performance for years to come.

Your Stock FA20 Power Baseline

The FA20 engine in your Subaru is a capable starting point. The naturally aspirated version in the BRZ comes from the factory with about 200 horsepower and 151 lb-ft of torque. The turbocharged FA20DIT found in the WRX from 2015 onward has a healthier output, but both are engineered with specific tolerances in mind. Think of this as your baseline. While you can add some power with bolt-on parts and a good tune, the stock pistons and connecting rods become the weak link when you start chasing bigger numbers. Pushing a stock block too far, especially with aggressive tuning or high boost, is a recipe for disaster.

The Role of Forged Pistons and Connecting Rods

If you want to make serious power, you have to strengthen the engine's core. This is where forged internals come in. The stock pistons and rods are typically cast, a process that is cost-effective for mass production but leaves them brittle under high stress. Forged components are created under immense pressure, resulting in a much denser and stronger structure. Upgrading to forged pistons and connecting rods is essential for any serious power build. These performance parts provide the durability needed to handle the increased cylinder pressures from higher boost and the stress of higher RPMs, giving you a reliable foundation for your power goals.

Real-World Power Limits of a Built FA20

With a built short block featuring forged internals, the power potential of the FA20 increases dramatically. A well-built and properly supported FA20 can reliably produce between 300 to 400 horsepower. Reaching these numbers isn't just about the block itself; it requires a holistic approach. You need to consider supporting modifications like an upgraded fuel system, a larger turbo, a more efficient intercooler, and a robust cooling system. Most importantly, achieving this power safely depends on professional engine tuning services. A skilled tuner will ensure all your components work in harmony, protecting your investment while maximizing its performance.

Breaking Down the Cost of an FA20 Short Block

Understanding the cost of an FA20 short block means deciding what you want your engine to do. Are you looking for a simple factory replacement, or are you building the foundation for serious power? The price difference between an OEM block and a built block reflects this choice, with each option catering to a completely different goal for your vehicle. Let's look at what you can expect to invest in either path.

The Price of an OEM Short Block

If you need a direct replacement for a failed engine with no plans for major power additions, an OEM short block is your go-to. A new FA20 DIT short block from Subaru typically costs around $2,700. For that price, you get a brand-new, factory-quality component that includes a new crankshaft, connecting rods, pistons, and bearings, all assembled to Subaru's specifications. This is the most straightforward option for getting your car back on the road in its original stock condition. It’s a reliable choice that restores your engine’s bottom end without any guesswork.

The Price of a Built Short Block

For enthusiasts looking to make significant power, a built short block is the necessary starting point. The pricing for these can start around the same as an OEM unit but can easily extend beyond $7,000. This wide range is determined by the quality of the components and the level of engineering involved. A block at the higher end of this scale is designed to handle the stress of a high-horsepower build, making it the perfect foundation for a track car or an aggressive street machine. These aren't just replacements; they are foundational performance parts engineered for durability.

Why Do Built Blocks Cost More?

So, what justifies the higher price of a built block? It all comes down to superior materials and advanced engineering. Instead of the cast components found in a stock engine, built blocks use forged pistons and connecting rods, which are far stronger and better at handling the intense heat and pressure of a high-output engine. Many premium built blocks also feature a closed deck design. This modification reinforces the cylinder walls, preventing them from flexing under high pressure. That added strength is what allows you to safely push your Subaru WRX upgrades and extract much more power than the factory setup could ever handle.

Choosing a High-Performance FA20 Short Block

Once you’ve decided to invest in a built FA20 short block, the next big step is choosing the right builder. This isn’t just about the parts inside; it’s about the expertise, engineering, and support that come with them. Not all built blocks are created equal, and picking a partner with a deep understanding of Subaru performance is the most important decision you’ll make for your build. Look beyond the spec sheet and consider the company’s history, their engineering philosophy, and the promises they make after the sale.

Why a Proven Track Record Matters

When you're trusting a company with the heart of your Subaru, their history matters. Look for builders with years, or even decades, of experience specifically with Subaru engines. A proven track record in motorsports, whether it's rally, time attack, or professional racing, is a strong indicator of quality. These high-stress environments are the ultimate testing ground for engine durability and performance. A company that has pushed its engines to the limit and back has learned invaluable lessons that directly translate to the reliability of the performance parts they offer you. This experience ensures they aren't just assembling parts; they're building on a foundation of proven success.

The Importance of In-House Engineering

The best engine builders are also innovators. A company with a dedicated in-house engineering team has complete control over quality and can develop proprietary solutions that you won't find elsewhere. For example, they can design reinforcements like a closed deck conversion to handle significantly more power than an open-deck block. This level of engineering means they can tailor solutions for specific platforms, whether you're building a high-horsepower Subaru WRX for the track or a reliable daily driver. When a builder engineers their own components and processes, you get a cohesive, purpose-built engine, not just a collection of off-the-shelf parts.

Look for a Warranty That Inspires Confidence

A warranty is more than just a policy; it’s a direct reflection of a builder's confidence in their work. A vague or limited warranty can be a red flag. You want to see a company that stands firmly behind its engines with clear terms. For example, a 12-month/12,000-mile warranty on a built short block is a powerful statement. It tells you the builder has faith in their components, their assembly process, and their quality control. This level of assurance is critical, especially when you're investing in a high-performance build. It also often goes hand-in-hand with expert support, including guidance on proper break-in and engine tuning services to protect your investment.

Your FA20 Short Block Buying Checklist

Buying a new short block is a major step in your build. It’s the foundation for all the power you plan to make, so you want to get it right. This checklist will walk you through the key decisions to ensure you choose a block that fits your car, meets your power goals, and gives you confidence for miles to come. Think of it as your guide to making a smart, informed investment in your Subaru's future performance. By taking a methodical approach, you can avoid common pitfalls and build a reliable engine ready for the street or the track.

Confirm Your FA20 Variant

First things first, you need to know exactly which FA20 engine is in your car. This might sound basic, but it's the most common point of confusion and the most critical detail to confirm. The FA20DIT, found in 2015 and newer Subaru WRX models, is different from the FA20D in the BRZ, Scion FR-S, and Toyota 86. While they share a name, their components are not always interchangeable. Verifying your specific engine variant ensures the short block you order is a perfect match, preventing costly and frustrating compatibility issues down the road. Double-check your vehicle's year and model before adding anything to your cart.

Decide on Internals and Deck Design

Once you know your variant, it's time to think about your power goals. This will determine the type of internals and block design you need. For high-horsepower builds, a block with a "closed deck" design is a must. This process reinforces the cylinder walls, making the engine significantly stronger and more reliable under intense pressure. You’ll also want to look for forged internals, specifically pistons and connecting rods. Unlike the stock cast parts, forged components are built to handle the increased stress from higher boost and aggressive tuning, making them essential for any serious performance parts build.

Review the Warranty and Support

A manufacturer's warranty speaks volumes about the quality of their work and the confidence they have in their product. A high-performance short block is a serious investment, and it should be protected by a solid guarantee. Look for a clear warranty that covers materials and workmanship for a reasonable period, like our 12-month/12,000-mile engine warranty. Beyond the warranty itself, consider the company's reputation for customer support. Are they accessible? Do they have a team of experts who can answer your questions? Choosing a builder who stands behind their work provides crucial peace of mind.

Plan for Professional Installation

Your new short block's performance and longevity depend heavily on proper installation. This isn't a simple weekend project. We always recommend having the work done by a reputable shop with experience building Subaru engines. A critical step is having your cylinder heads inspected and resurfaced by a machine shop to ensure a perfect seal. Your entire oiling system, including the oil cooler and banjo filters, must also be thoroughly cleaned or replaced to prevent contamination. Professional engine tuning services are also essential after installation to dial in the engine and ensure everything runs safely and efficiently.

Installing Your New FA20 Short Block

Once your new FA20 short block arrives, the real fun begins. Proper installation is just as important as the quality of the block itself. Taking your time here and paying attention to the details will protect your investment and set your engine up for a long, powerful life. Whether you’re tackling this yourself or working with a trusted shop, these are the critical steps that can't be overlooked.

Prepping Your Heads and Timing Components

Before you can marry your cylinder heads to the new block, they need to be spotless. Any leftover gasket material, oil, or grime on the mating surfaces can compromise the seal and lead to frustrating leaks down the road. A perfectly clean surface is essential for a proper head gasket seal. While the engine is apart, it’s also the perfect time to inspect your timing components. Check the timing chains, guides, and tensioners for any signs of wear. Replacing them now is a smart move that can save you from major headaches later.

Ensuring Oil System Health and Proper Torque

Your new engine’s first breath of life will be its oil. Before that first startup, you must install a new oil filter and fill the crankcase with the correct type and amount of high-quality oil. Beyond that, precision is key when it comes to reassembly. You’ll need a reliable torque wrench to tighten the head bolts according to the manufacturer's specifications. Following the correct torque sequence and values ensures even pressure across the head gasket, which is critical for preventing failure, especially in a high-performance build. Don't guess on this step; get it right.

The First 1,000 Miles: Break-In and Tuning

The first 1,000 miles on your new engine are the most important of its life. This is the break-in period, where the piston rings seat against the cylinder walls. During this time, you need to vary the engine's RPM and avoid putting it under heavy load, so no full-throttle pulls or track days just yet. A proper break-in procedure is your best bet for ensuring everything settles in correctly. After the break-in is complete, it’s time for the final piece of the puzzle: a professional tune. Our expert engine tuning services will calibrate your ECU to the new hardware, optimizing performance and ensuring your engine runs safely and efficiently for years to come.

Building Around Your New Short Block

Dropping in a new short block is a huge step, but it’s really just the foundation of your build. To get the reliable power you’re after, you need to make sure the rest of your engine components can keep up. Think of it like building a house: a strong foundation is critical, but it’s the framework, plumbing, and electrical systems that make it a functional home. The same principle applies here; your supporting mods are what will truly bring your new FA20 to life.

Essential Supporting Mods for Maximum Power

A built short block is designed to handle more power, but it can’t create that power on its own. To make bigger numbers, your engine needs to breathe better and get more fuel. Upgrading your intake and exhaust systems is the first step to improving airflow, which is essential for getting the most out of your new block. From there, you’ll need to address the fuel system. A high-performance fuel pump and injectors are necessary to ensure your engine gets the fuel it needs, especially as you push for higher horsepower. Without enough fuel, you risk running lean, which can lead to catastrophic engine damage. Planning these performance parts upgrades alongside your short block installation ensures a balanced and powerful setup from day one.

Upgrading Your Oil, Turbo, and Cooling Systems

More power means more heat, and managing that heat is key to your engine’s longevity. Your stock oil and cooling systems were designed for stock power levels, so they need attention. A high-quality oil cooler helps maintain stable oil temperatures, which is crucial during spirited driving or on track days. We also highly recommend an Air/Oil Separator (AOS) to prevent oil from contaminating your intake tract. When it comes to the turbo, many builders see the short block as an opportunity to upgrade to a larger unit for significant power gains. Just remember that a bigger turbo must be matched with the right supporting mods to work efficiently and safely.

Protect Your Investment with Smart Maintenance

You’ve just made a significant investment in your Subaru’s heart, so protecting it should be a top priority. This starts with diligent maintenance. Following a proper break-in procedure is non-negotiable. After that, routine oil changes with high-quality synthetic oil will keep your engine running smoothly. You should also regularly check your coolant levels and ensure the entire cooling system is in top shape to prevent overheating. Finally, a professional tune is not just a suggestion; it’s a requirement. A proper engine tuning service will dial in your air-fuel ratios and timing, ensuring your engine operates safely and makes reliable power for years to come.

Related Articles

• FA20 Long Block: Everything You Need to Know
• Subaru FA20 OEM+ Short Block for BRZ/FR-S/GT86 | Crawford Performance

Frequently Asked Questions

Is a built short block really necessary, or can I just get an OEM one? This is the most important question, and the answer depends entirely on your goals. If you just need to replace a failed engine and plan to keep your car at or near stock power levels, an OEM short block is a perfectly reliable and cost-effective choice. However, the moment you decide you want to make more power, a built block becomes essential. It's engineered with stronger, forged components that provide the durability needed to handle the increased stress from a larger turbo, higher boost, and aggressive tuning.

What's the difference between the FA20D (BRZ) and FA20DIT (WRX) short blocks? While they share the FA20 name, these are two very different engines designed for different purposes. The FA20DIT in the WRX is built for forced induction and has lower compression pistons to handle turbo boost. The FA20D in the BRZ is naturally aspirated and uses higher compression pistons to maximize efficiency and response without a turbo. You cannot swap them. Ordering the correct block for your specific model is the most critical first step in your build.

What does "closed deck" mean, and do I actually need it? The factory FA20 block has an "open deck" design, which means there are open passages for coolant around the tops of the cylinder walls. This is fine for stock power, but under high boost, these unsupported walls can flex or even crack. A closed deck modification adds metal bracing to support the cylinder walls, making the entire block structure significantly stronger. If you are planning a high-horsepower build (approaching 500 horsepower or more), a closed deck block is not just a good idea; it's a necessary safety measure for engine reliability.

Is a new short block the only thing I need to make more power? A built short block is the strong foundation, but it doesn't create power on its own. To achieve higher horsepower, you need to build a complete system around it. This means your engine needs more air, more fuel, and better cooling. You should plan for upgrades to your fuel pump and injectors, intake and exhaust systems, and your oil and coolant systems. A larger turbo is also a common part of the equation. Thinking of these as a complete package will ensure all your components work together to create reliable power.

What is the most important thing to do after my new short block is installed? The two most critical steps after installation are the break-in period and the final tune. The first 1,000 miles are crucial for seating the new piston rings and bearings, which requires varying your engine speed and avoiding heavy loads. After the break-in is complete, you must get a professional engine tune. A skilled tuner will calibrate your car's computer to the new hardware, optimizing the air-fuel ratio and timing to ensure your engine makes power safely and reliably for years to come.