Forged FA20 Short Block: The Ultimate Guide

There’s a certain anxiety that comes with pushing a modified car hard. You listen for every unusual noise, wondering if this is the pull that will be one too many for your stock engine. That fear can take the fun out of driving. The ultimate solution for this peace of mind is building an engine that you know can handle the abuse. This is precisely why enthusiasts upgrade to a forged internal FA20 short block. It’s not just about making more power; it’s about creating reliable power. By reinforcing the engine’s core with stronger components, you can confidently enjoy track days and spirited drives without worrying about catastrophic failure.

Key Takeaways

• Build a Strong Foundation for Power: A forged short block is the essential first step for any build aiming to surpass the stock engine's limits, providing the strength needed to reliably handle the stress of high horsepower and torque.
• Plan for Essential Supporting Mods: A forged block requires a systems-based approach; upgrading your fuel, cooling, and oiling components is necessary to support the new engine and achieve a balanced, high-performance build.
• Protect Your Investment with a Professional Tune: The final, non-negotiable step is a professional engine tune, which synchronizes all your new hardware, optimizes performance, and ensures the long-term health and safety of your built engine.

What Is a Forged FA20 Short Block?

If you're looking to get serious power out of your Subaru, you’ve probably heard the term "forged short block." But what exactly is it? Think of the short block as the foundation of your engine; it’s the entire bottom half, containing the crankshaft, connecting rods, and pistons. A forged FA20 short block is a high-performance version of this foundation, specifically built to handle much more power and stress than the original factory engine. It’s a common and essential upgrade for Subaru models with the FA20 engine, including the WRX, Forester XT, and BRZ.

The "forged" part of the name refers to the manufacturing process of its internal components. Instead of using standard cast parts, a forged block uses components made from solid billets of metal that are heated and pressed into shape under immense pressure. This process creates incredibly dense and strong parts, eliminating the microscopic weak points found in cast components. Upgrading to a forged short block is the first major step in transforming your car from a daily driver into a high-performance machine ready for the track or demanding driving conditions. It’s the core of any serious engine build and provides the strength needed for significant performance parts upgrades.

Forged vs. Stock: What's the Difference?

The main difference between a forged and a stock short block comes down to strength and durability. Your Subaru’s stock engine components are typically "cast," meaning molten metal is poured into a mold. This is a cost-effective method for mass production, but it can leave behind tiny air pockets and imperfections that create weak points. When you start adding more power with a bigger turbo or an aggressive tune, these weak points are where failures often happen.

A forged short block replaces those cast internals with much stronger forged ones. This often involves using the original engine casing but fitting it with aftermarket forged pistons and connecting rods. Because forged parts are created from a single piece of metal under extreme pressure, they are far denser and more resilient. This allows your engine to safely handle higher cylinder pressures, increased RPMs, and the overall stress that comes with making more horsepower.

A Look Inside: Key Forged Components

When we talk about "forged internals," we're referring to a few key parts that take the most abuse inside your engine. The most critical upgrades in a forged FA20 short block are the pistons and connecting rods. Forged pistons are designed to withstand the intense heat and pressure of high-combustion environments without cracking or melting. They are the heart of a strong engine build.

Equally important are the connecting rods, which link the pistons to the crankshaft. Under high power, stock rods can bend or even snap, causing catastrophic engine failure. Forged connecting rods, like those from trusted brands such as Carrillo, provide the strength needed to handle the massive forces of a modified engine. Many builds also include upgraded performance bearings, which reduce friction and wear on the rotating assembly, ensuring your engine runs smoothly even under extreme loads. These are the Subaru WRX upgrades that build a reliable foundation for power.

Open Deck vs. Closed Deck Designs

Another important factor in a forged short block is its deck design. The FA20 engine comes from the factory with an "open deck," where the coolant passages around the cylinders are open at the top surface of the block. This design is great for cooling in a stock vehicle, but it leaves the cylinder walls unsupported. When you introduce high levels of boost, this lack of support can allow the cylinders to flex or even crack.

For high-horsepower builds, a "closed deck" conversion is the solution. This process adds a reinforcing plate to the top of the block, closing the open coolant passages and creating a solid, rigid structure around the cylinders. A closed deck design provides maximum support for the cylinder walls, allowing the engine to handle significantly more power, often up to 800 horsepower or more. This modification is essential for anyone planning a serious track or race build and requires professional engine tuning services to maximize its potential.

Why Upgrade to a Forged FA20?

Deciding to upgrade to a forged FA20 short block is a major step for any Subaru owner. It’s the line between enjoying a fun daily driver and building a true performance machine. While the stock FA20 is a capable engine for everyday use, it has inherent design limits that become apparent when you start chasing significant power gains. If your goal is to move beyond simple bolt-ons and truly transform your vehicle’s performance, a forged short block is the foundation you need to build upon. It’s about creating a durable, reliable engine that can handle the stress of higher horsepower and torque without compromise.

The Limits of a Stock FA20 Engine

The stock FA20 engine in your WRX or BRZ is engineered for a balance of performance, efficiency, and longevity under normal driving conditions. However, when you start adding modifications to increase power, you’ll quickly find its ceiling. The primary limitation lies in the stock internal components, like the pistons and connecting rods, which are cast rather than forged. These parts can become a failure point under the increased cylinder pressure and stress from higher torque levels. Pushing a stock block much past 350-400 wheel horsepower is a gamble. For reliable power at that level and beyond, upgrading to stronger, forged internals is not just recommended; it’s essential for engine safety and your peace of mind.

Common Failure Points to Watch For

When you increase an engine's output, you expose the weakest links in the entire drivetrain. With the FA20, pushing for high power on a stock block often leads to predictable issues. The connecting rods are a known weak point and are often the first component to fail under high torque. Beyond the engine itself, the stock transmission may struggle to handle the increased load, especially if you’re aiming for power goals above 400 horsepower. To build a balanced and reliable car, you have to think systemically. This means considering upgrades to your cylinder heads, valve springs, and fuel system, all tied together with professional engine tuning services to ensure every component works in harmony.

Debunking Myths About Stock Block Strength

You’ve probably heard the term "stock block with forged internals" in forums and car groups, and it can be a bit misleading. This phrase doesn't mean the original, untouched block is suddenly capable of handling immense power. Instead, it typically refers to using the original engine casing, or "case halves," while replacing all the critical internal components. The real strength comes from the new forged pistons, connecting rods, and upgraded bearings inside that casing. The block itself is simply the housing. Understanding this distinction is key, as it clarifies that the durability for your high-power build comes from quality performance parts, not from any hidden strength in the factory block.

Performance Gains from a Forged Short Block

Upgrading to a forged FA20 short block is one of the most significant steps you can take to transform your Subaru's performance. While the stock engine is capable, it has its limits, especially when you start adding more power. A forged block isn't just about chasing huge horsepower numbers; it's about building a stronger, more resilient foundation for your entire engine setup. This upgrade provides a trifecta of benefits: it allows you to safely run more power, it increases the engine's durability under stress, and it ultimately protects your investment by creating a more reliable powerplant for the long haul. Whether you're aiming for a high-performance street car or a dedicated track machine, a forged short block is the key to achieving your goals without constantly worrying about engine failure.

Handle More Horsepower and Torque

The most obvious reason to upgrade is the massive increase in power handling. A stock FA20 block can be a liability when you push past a certain point, but a forged short block is built specifically for high-output applications. Thanks to stronger pistons, connecting rods, and a robust crankshaft, these blocks are engineered to withstand the immense pressures of high boost and aggressive tuning. Some forged FA20 builds are rated to handle up to 650 horsepower, a figure far beyond what the stock internals could ever safely manage. This gives you the headroom to install larger turbos, upgrade your fuel system, and truly explore the performance potential of your Subaru. It's the confidence you need to add serious performance parts without risking catastrophic engine damage.

Improve Heat and Stress Resistance

High-performance driving generates a tremendous amount of heat and mechanical stress, both of which are enemies of a stock engine. The forging process creates components with a denser grain structure than the stock cast parts, making them inherently stronger and better at dissipating heat. This improved thermal stability helps prevent piston ring land failure, a common issue in modified FA20 engines. Components like forged connecting rods and high-performance bearings are designed to endure the extreme forces of high-RPM operation. This means your engine can better withstand the rigors of a track day or spirited canyon run, maintaining its integrity when pushed to the limit. This added resilience is crucial for anyone serious about building a durable, high-powered Subaru WRX.

Extend Your Engine's Lifespan

While it might seem counterintuitive, investing in a high-performance forged block can actually extend the life of your modified engine. By replacing the stock engine's weakest links with superior components, you create a much more durable foundation. A properly assembled forged short block, built with meticulous quality checks, is designed for longevity under power. It provides a stable base that can handle future upgrades without failing. However, the block is just one piece of the puzzle. To ensure a long and healthy life for your new engine, it's absolutely critical to pair it with essential supporting mods and, most importantly, a professional tune. A proper engine tuning service will optimize your engine's parameters to work harmoniously with the new hardware, ensuring both maximum performance and long-term reliability.

How Much Power Can a Forged FA20 Handle?

Upgrading to a forged FA20 short block is the single most effective step you can take to prepare your Subaru for serious power. While the stock engine has its limits, a forged block provides the robust foundation needed to withstand significantly higher horsepower and torque. The ultimate power your engine can handle, however, isn't a single number. It depends on a combination of factors, including your specific components, supporting modifications, and whether your build is naturally aspirated or uses forced induction.

Think of the forged short block as the strong backbone of your high-performance build. It’s designed to manage the intense pressures and temperatures that come with increased power, but it works as part of a larger system. Your fuel system, turbocharger, cooling setup, and especially your engine tune all play critical roles in determining the final, reliable output. Getting this combination right is the key to building an engine that not only produces impressive numbers but also delivers consistent, dependable performance on the track or trail.

Power Limits: Naturally Aspirated vs. Forced Induction

The type of induction you use creates a major fork in the road for your power potential. For a naturally aspirated (NA) build, a forged short block adds incredible durability and allows the engine to rev higher and more safely. However, since an NA engine's power is limited by how much air it can naturally breathe, the horsepower gains will be modest. The primary benefit here is creating a bulletproof engine for high-RPM applications.

Forced induction is where a forged FA20 truly comes alive. By adding a turbocharger or supercharger, you are forcing more air into the cylinders, which creates much higher internal pressures. A stock block can't handle this for long, but a forged block is built for it. Even with forged internals, reaching extreme torque figures requires a well-thought-out setup. Pushing for 450 lb-ft of torque reliably often demands more than just a forged block; it requires a complete system of performance parts working in harmony.

Setting Realistic Power Goals for Your Build

Before you start buying parts, it’s important to set a realistic power goal that aligns with your car's intended use. Are you building a spirited daily driver, a weekend track weapon, or an all-out race car? Your answer will guide your component choices. For many Subaru WRX owners, a reliable and thrilling goal for a street or track build with a quality turbo and a forged short block is in the low-to-mid 400s for both horsepower and torque. This range delivers a massive performance improvement without sacrificing too much drivability.

If your ambitions are higher, you’ll need to invest in even stronger components. Some manufacturers offer staged blocks designed for specific power targets, such as 600 or 800 horsepower, often using closed-deck designs for maximum strength. Achieving these numbers safely and reliably depends entirely on a professional tune. Expert engine tuning services will ensure your engine’s parameters are perfectly dialed in to match your hardware.

Key Metrics to Measure Performance

While peak horsepower is an exciting number, it doesn't tell the whole story. A truly great build is measured by more than just one metric. You should also focus on the torque curve, the width of the powerband, and overall reliability. A car with a broad, flat torque curve will feel much faster and be more usable on a track than a car with a high horsepower number that only appears at the very top of the rev range.

A well-assembled forged FA20 short block from a reputable builder can often handle up to 650 horsepower, but this is a benchmark, not a guarantee. The final capability is determined by the quality of the individual components, the precision of the assembly, and the effectiveness of your supporting mods. When evaluating a build, look beyond the peak numbers and consider how the power is delivered. The goal is to create a balanced, responsive, and durable engine that inspires confidence every time you turn the key.

Customizing Your Forged FA20 Short Block

Building a forged short block is more than just assembling stronger parts; it’s about creating a combination that perfectly matches your performance goals. Whether you're building a responsive daily driver or a dedicated track car, every component choice matters. Customizing your FA20 allows you to define its powerband, durability, and overall character. The key is to make informed decisions on core elements like compression ratio, internal components, and supporting systems to ensure everything works together seamlessly.

Choose the Right Compression Ratio

Your compression ratio is a foundational choice that dictates how your engine will behave. Think of it as the amount of "squeeze" your pistons put on the air-fuel mixture before ignition. For an FA20, this decision hinges on whether you plan to use forced induction. If you're adding a turbocharger or supercharger, a lower compression ratio (around 10.5:1) is the way to go. This gives you a greater margin of safety against engine knock (detonation) under high boost. For a naturally aspirated build, sticking with a higher, stock-like ratio (around 12.5:1) will maximize efficiency and throttle response. Getting this right is critical for a successful engine tuning service and a reliable build.

Select Your Connecting Rods and Pistons

The connecting rods and pistons are the heart of your engine's rotating assembly, and they take the brunt of the force from combustion. Stock components are typically cast, which is fine for factory power levels, but they become a major weak point in a performance build. Upgrading to forged pistons and rods provides the strength needed to handle significantly more power and abuse. When selecting these performance parts, consider your ultimate horsepower target. A 400-horsepower street build has different needs than an 800-horsepower track machine, so choose components rated appropriately for your goals to ensure long-term reliability.

Consider Bearing and Oiling Upgrades

Engine bearings and proper lubrication are the unsung heroes of a high-performance build. Stock bearings can fail under the increased loads of a modified engine, leading to catastrophic failure. Upgrading to performance-grade bearings from trusted brands provides a more durable surface that can withstand higher stress and heat. Equally important is addressing the FA20’s oiling system. To prevent oil starvation during aggressive driving, consider installing an Air/Oil Separator (AOS) and a baffled oil pan. These Subaru WRX upgrades ensure your engine receives a consistent supply of clean oil, protecting your investment when you push it hard on the street or track.

How to Choose the Right Forged Short Block

Selecting the right forged short block is one of the most critical decisions you'll make for your Subaru build. This isn't just another part; it's the foundation of your engine's performance and reliability. A well-chosen short block will support your power goals for years, while the wrong one can lead to frustration and costly repairs. The key is to find a balance between your performance ambitions, the quality of the components, and the builder's expertise.

Think of it as creating a blueprint for your engine. You need to consider how much power you realistically want to make, how you plan to use your car, and what supporting modifications you have or plan to install. Whether you're building a responsive daily driver, a high-horsepower track machine, or a rugged overlanding rig, the short block needs to be up to the task. We'll walk through the essential factors to consider, from power ratings and build quality to component selection and warranty, so you can make an informed decision with confidence.

Evaluating Power and Torque Ratings

When you look at a forged short block, its power and torque ratings are the headline specifications. These numbers aren't just for bragging rights; they represent what the block is engineered to handle reliably. Some blocks are rated for up to 650 horsepower, making them ideal for aggressive track or drag racing builds. Others might be rated for a more moderate figure, perfect for a spirited street car that still needs to be dependable.

Your job is to match the block's rating to your ultimate power goals. Don't just think about the power you have now, but where you want your build to end up. Choosing a block that slightly exceeds your target provides a safety margin and room to grow. This ensures you won't be pushing the components to their absolute limit, which is key for engine longevity and peace of mind.

Assessing Build Quality and Assembly Process

The quality of a forged short block goes far beyond the parts inside it. The assembly process itself is a critical factor that separates a reliable engine from a ticking time bomb. Reputable builders assemble their short blocks in meticulously clean environments to prevent any contaminants from compromising the engine's integrity. Every clearance, tolerance, and torque specification is precisely measured and documented.

This level of detail is what ensures all the high-performance components work together harmoniously. When you're investing in a forged engine, you're also investing in the builder's expertise and process. Ask about their assembly methods and quality control. A builder who is proud of their precision and cleanliness is one you can trust to construct the heart of your vehicle.

Comparing Component Brands and Materials

Diving into the spec sheet of a forged short block can feel like reading a different language, but it's where you'll find the most important details. Look at the specific brands and materials used for the core components: the pistons, connecting rods, and bearings. High-quality performance parts from trusted manufacturers are a strong indicator of a durable build.

You'll also want to check the compression ratio. A lower compression ratio, such as 10.5:1, is often better for forced induction builds (turbo or supercharger) as it helps prevent detonation under high pressure. Understanding these specifications will help you compare different blocks and choose one with components that are perfectly matched to your Subaru's setup and your performance goals.

The Importance of a Warranty and Support

A forged short block is a major investment, and it should come with protection and support. A manufacturer's warranty is a direct reflection of their confidence in their product. At Crawford Performance, we stand behind our work with a 12-month/12,000-mile warranty on our engines, providing you with crucial peace of mind.

Beyond the warranty, consider the level of support you'll receive. Can you easily get in touch with an expert if you have questions during installation or tuning? A company that offers comprehensive support, including professional engine tuning services, demonstrates a commitment to your success. This ongoing relationship ensures you have a partner throughout your build, not just a part in a box.

The Cost of a Forged FA20 Short Block

Investing in a forged FA20 short block is a serious commitment to performance, and the price reflects the engineering, materials, and labor involved. While it's a significant upgrade, understanding the costs helps you plan a build that matches your goals and budget. Prices for a pre-assembled forged short block typically start around $5,000 and can climb past $7,000, depending on the components and the builder.

This price tag covers the assembled bottom end of your engine, which includes the engine block, crankshaft, connecting rods, and pistons. It’s important to remember this cost doesn't include other necessary components like cylinder heads, a new turbo, or the labor for installation and tuning. Think of the short block as the reliable foundation upon which the rest of your high-horsepower build will stand. The investment ensures your engine can handle the power you intend to throw at it, safeguarding you from the catastrophic failure of a stock block pushed beyond its limits.

Entry-Level vs. High-End Build Costs

When you start shopping for a forged short block, you'll see terms like "Stage 1" or "600 HP" builds. An entry-level forged block, often priced between $5,000 and $6,000, is far from basic. These setups are typically rated to handle up to 650 horsepower, providing a massive improvement in strength over the stock engine. They are perfect for most street and track enthusiasts who want a durable build with plenty of headroom for future power increases.

High-end builds, which can cost $6,500 or more, are designed for those chasing maximum power. The extra cost usually accounts for a closed-deck block conversion for superior cylinder wall strength, along with premium-grade connecting rods and pistons. These blocks are engineered to withstand the extreme pressures of high-boost applications and are the go-to choice for competitive racing or builds pushing 800 horsepower and beyond.

What Factors Influence the Price?

The price of a forged short block is a direct reflection of the quality and strength of its components. The single biggest factor is the selection of internal performance parts. High-end forged pistons, robust H-beam or I-beam connecting rods, and performance bearings from top-tier brands contribute significantly to the cost but are essential for reliability under pressure.

Another major factor is the engine block itself. A standard open-deck block is less expensive than a reinforced closed-deck block, which requires precise machining to strengthen the cylinder walls. Customizations like your chosen compression ratio can also affect the price, as it may require specific piston designs. Finally, the builder's expertise and assembly process are built into the cost. A meticulously assembled and blueprinted engine from a reputable builder ensures proper clearances and reliable performance.

Essential Supporting Mods for Your Forged Block

Installing a forged FA20 short block is a serious commitment to performance, but it’s only the first step. Think of the forged block as a strong foundation; to build a powerful and reliable engine, you must also upgrade the supporting systems that surround it. Simply dropping a built block into a stock car without addressing the fuel, cooling, and engine management systems is a recipe for leaving power on the table and, worse, risking the health of your new investment. To truly get the most out of your forged engine, you need to ensure every component can handle the increased demands of higher horsepower and torque. These supporting modifications aren't just recommended, they are essential for creating a balanced and durable performance build.

Fuel System and Turbocharger Upgrades

Once your engine is built to handle more power, you need to supply it with enough fuel and air to actually create it. The stock fuel system is only designed to support factory horsepower levels. When you aim for power goals of 450 lb-ft of torque or 500+ hp, upgrading your fuel pump and injectors becomes critical. A high-pressure fuel pump (HPFP) ensures your engine receives the volume of fuel it needs under heavy load. This works hand-in-hand with a larger turbocharger, which forces more air into the cylinders. Matching these performance parts is key to maintaining a safe air-fuel ratio and preventing a lean condition that can cause catastrophic engine damage.

Critical Cooling and Oiling Enhancements

More power generates more heat, and managing that heat is one of the most important jobs in a high-performance build. The stock top-mount intercooler can quickly become overwhelmed, leading to heat soak and a loss of power. Upgrading to a larger front-mount intercooler (FMIC) provides significantly better cooling for the charged air entering your engine. Equally important is the oiling system. To protect your investment, an Air/Oil Separator (AOS) is a must-have. The Crawford Performance AOS prevents oil blow-by from contaminating your intake and lowering your fuel's octane rating, ensuring your engine breathes clean air and maintains consistent performance, especially under track conditions.

The Necessity of a Professional Tune

After you’ve installed your forged block and all the supporting hardware, the final and most crucial step is a professional tune. Your vehicle's Engine Control Unit (ECU) is calibrated for the stock components, and it has no idea how to manage the new, higher-flowing parts you’ve just installed. A professional tuner will recalibrate the ECU to optimize fuel and ignition timing for your specific setup. This process ensures your engine runs efficiently, makes the most power possible from your upgrades, and operates safely within its new limits. Skipping a professional tune is not an option; it’s the only way to tie everything together and protect the thousands of dollars you’ve invested in your Subaru WRX upgrades and engine build.

Is a Forged FA20 Short Block Right for Your Build?

Deciding whether to invest in a forged FA20 short block comes down to one thing: your goals. It’s a significant upgrade, and while it’s the foundation for any serious power build, it isn’t necessary for every Subaru owner. The right answer for you depends entirely on what you want to achieve with your vehicle. If you’re chasing big power numbers, building a dedicated track car, or simply want the peace of mind that comes with a bulletproof engine, then a forged block is likely the right path.

First, take a hard look at your power goals. A stock FA20 engine is great for daily driving and light modifications, but it has its limits. If your plans include a larger turbocharger or supercharger with the goal of pushing past 400 horsepower, a forged short block becomes less of a want and more of a need. Forged internals are specifically engineered to handle the immense stress and heat that come with high-horsepower applications, with some builds capable of handling up to 600 BHP. If you’re aiming for that level of performance, you’re asking for more than the stock components were ever designed to give.

Next, consider the rest of your build plan. A forged short block doesn't work in a vacuum. To truly take advantage of its strength, you need to pair it with other high-quality performance parts. Reaching high power and torque levels reliably requires a holistic approach. This means you should also be planning for upgrades to your fuel system, a front-mount intercooler, and potentially built cylinder heads to support the new block. Most importantly, a professional tune is absolutely critical. An expert tune ensures all your new components work together harmoniously and safely, protecting your investment. Without proper engine tuning services, you risk damaging the very engine you sought to fortify.

Ultimately, a forged FA20 is for the enthusiast who is pushing their car beyond its factory specifications. It’s for the driver who wants to hit the track on the weekend without worrying about engine failure. It’s for the builder creating a high-horsepower street machine or a rugged overlanding rig that needs to be dependable under extreme conditions. If your vision for your Subaru involves adding significant power and you understand it’s a foundational part of a larger system of upgrades, then a forged short block is an excellent and necessary investment in your build’s performance and longevity.

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Frequently Asked Questions

Do I really need a forged block if I'm just doing basic mods? For most daily drivers with simple bolt-on parts like an intake or cat-back exhaust, your stock FA20 engine is perfectly adequate. The conversation about a forged short block begins when your goals involve making significant power. If you plan to install a larger turbo or push your engine past the 350-400 wheel horsepower range, a forged block becomes essential for reliability. It’s an investment in making that power safely without risking the catastrophic failure of stock components.

What other parts must I upgrade along with the forged short block? A forged short block is the strong foundation, not the entire house. To support the block’s ability to handle more power, you must also upgrade the systems around it. This includes a more capable fuel system (injectors and a high-pressure fuel pump) and a larger turbocharger to supply the necessary air. You will also need cooling upgrades, like a front-mount intercooler and an Air/Oil Separator, to manage heat and protect the engine. Finally, a professional tune is not optional; it’s the critical step that synchronizes all these new parts to work together safely and effectively.

Will a forged block make my car less reliable for daily driving? Quite the opposite, when done correctly. A professionally assembled forged short block paired with a proper tune can be more reliable than a stock engine that is constantly being pushed to its breaking point. The forged internals are specifically designed to handle the stress of high power, which provides a much larger safety margin. The key to long-term reliability is the quality of the build and the expertise of the engine tuner, who ensures the car runs smoothly and safely under all conditions, not just at full throttle.

What's the main benefit of a closed-deck block over an open-deck one? Think of your engine’s cylinder walls like the walls of a building. The stock FA20 has an open-deck design, which leaves the tops of these walls unsupported. This is fine for stock power, but under the extreme cylinder pressures of a high-horsepower build, these walls can flex or even crack. A closed-deck conversion adds a metal plate to the top of the block, reinforcing those walls. This modification provides the structural integrity needed for builds aiming for 600 horsepower and beyond.

How do I choose the right compression ratio for my build? The right compression ratio depends entirely on how you plan to make power. If you are building an engine for forced induction (using a turbocharger or supercharger), a lower compression ratio, around 10.5:1, is the standard choice. This lower ratio provides a greater safety margin against engine knock when running high levels of boost. For a naturally aspirated build, a higher compression ratio, closer to the stock 12.5:1, is ideal because it maximizes engine efficiency and throttle response.