EJ25 Built Long Block: The Complete Buyer's Guide

Every Subaru owner has a number in mind. Maybe it's a reliable 400 horsepower for a daily driver, or 500-plus for a track car. A bigger turbo and an aggressive tune can produce peak numbers, but they don't guarantee the engine survives them. A built EJ25 long block is the foundation: it replaces the stock motor's known weak points with components built for the load. This guide covers what a built long block is, what it can handle, and the supporting parts you need to get there safely.

What Is a Built EJ25 Long Block?

A built EJ25 long block is a complete engine assembly built to handle more power and stress than the factory engine. It includes the block, crankshaft, pistons, and connecting rods, plus the cylinder heads and the valvetrain — camshafts, valves, and springs. Weaker factory components are replaced with stronger forged parts, so the engine is prepared for higher cylinder pressure and harder use.

Long Block vs. Short Block: Key Differences

A short block is the bottom end: the block, crankshaft, connecting rods, and pistons, assembled. It's only half the engine.

A long block includes the entire short block assembly plus the cylinder heads, camshafts, and valvetrain components. Choosing a Crawford Performance Subaru long block means the top and bottom ends are matched and assembled as one unit. That removes the work of sourcing and assembling heads yourself, reduces compatibility risk, and simplifies installation.

Built vs. Stock: Why It's an Upgrade

The stock EJ25 uses cast pistons. They are fine at factory power levels. Under the added heat and pressure of a higher-output build, they become the weak point. A stock EJ257 is reliable to about 350 whp; past that, the cast pistons' ringlands are the failure point.

A built engine uses forged pistons and connecting rods. Forging makes the components denser and more durable, so a built EJ25 can reliably handle 400 horsepower and beyond — and sustain it without giving up longevity.

The Stock EJ25's Weak Points

The EJ25 powers the WRX and STI, and it's a strong platform at stock power. Push past its original intent and three limitations show up: the pistons, the head gaskets, and oil consumption under stress. Each can cascade into bigger damage if it isn't addressed. A built engine reinforces all three.

Ringland Failure

Ringland failure is the most common failure when adding power to a stock EJ25. The ringlands are the sections of the piston that hold the rings in place. In the stock engine they're cast aluminum alloy — adequate at factory power, brittle under the increased cylinder pressure of more boost or aggressive tuning. They crack or break off, costing compression, increasing oil consumption, and risking catastrophic damage. Forged pistons are the cornerstone fix, standard in any serious EJ25 build.

Head Gasket Issues

The head gasket seals the block to the heads, keeping combustion pressure, coolant, and oil in their own channels. When it fails, fluids mix — overheating, white smoke, and worse follow. The problem was more prevalent in older, naturally aspirated models, but no EJ25 is immune, especially at performance temperatures and pressures. Correct assembly and a professional tune keep the heads sealed.

Oil Consumption Problems

The EJ25 consumes oil when driven hard because the factory crankcase ventilation system pulls oil vapor into the intake tract. That oil burns during combustion, lowering the oil level and coating the intake valves and pistons with carbon. Over time it lowers the fuel's effective octane rating and raises the risk of detonation.

An Air/Oil Separator (AOS) is one of the most effective reliability upgrades you can make. It captures the oil vapor and returns it to the crankcase, so only clean air enters the engine. Crawford developed the original closed-loop Subaru AOS. Ours is aluminum, made in the USA, and drains back automatically. It carries no CARB EO — check the EO status for your application.

Key Features of a Reliable Built EJ25 Long Block

A built engine isn't a collection of expensive parts. It's a balanced system where each component is chosen to work with the rest.

Forged Pistons, Rods, and Crankshaft

The rotating assembly takes the most abuse, and stock cast components are the known failure point when power goes up. A built long block replaces them with forged parts that handle the increased cylinder pressures of higher output. Crawford's built engines use CrawfordSPEC forged pistons, made by JE Pistons, matched to the engine's rating. Crawford builds on brand-new OEM blocks only. No core is required, there is no core charge, and there is no core return. Short blocks and long blocks are both available.

Upgraded Cylinder Heads

Upgraded heads and camshafts improve airflow, so the engine breathes more efficiently and makes more power and torque across the rev range without losing low-end response — a wider, more usable powerband instead of a single peak number.

On a Crawford long block, heads are a choice. The head packages are:

• Rebel — the street package: cleaning, damage inspection, precision valve work, and resurfacing. Built for a daily driver or light track use with moderate turbo upgrades.
• Bandit — everything in Rebel, plus professional port and polish work. For a powerful street car and weekend track days.
• Outlaw — hand-finished, race-spec porting with custom valve seats. For engines pushing over 700 horsepower.

Crawford's Street Spec heads use a 3-angle valve job and support builds up to 500 whp.

High-Performance Bearings and Seals

Bearings and seals aren't glamorous, but they're critical. Under high-output stress, factory bearings can wear prematurely or fail, and that failure is catastrophic. Upgraded bearings use stronger materials built for more stress and heat. Quality seals and gaskets prevent leaks. These details separate a reliable engine from a short-lived one.

Built EJ25 Power Potential: How Much Can It Handle?

There is no single number. What a built engine can handle depends on the quality of its components, the builder, and your goals. Decide how much power you actually need before you pick an engine.

Setting Power Goals for Your Build

Be honest about how you'll use the car. A 600-horsepower daily driver sounds fun; driving it in traffic is a different reality from a 400-horsepower build focused on smooth, reliable performance.

The Ratings That Matter

Crawford states power through its engine ratings, and that's the only basis to shop on:

• CrawfordSPEC CSS 540 — 450 whp / 540 bhp
• CrawfordSPEC CCR 660 — 550 whp / 660 bhp
• CrawfordSPEC CRS 720+ — 600+ whp / 720+ bhp

The legacy stage-named EJ blocks keep their names and ratings: the S2 at 450 whp, the S3L-X at 550 whp, and the S3L-X FSR at 600+ whp.

Against that line, the baseline: stock is reliable to about 350 whp. Past that on stock internals, you're asking for ringland failure. An entry-level forged-piston build reliably handles 400 whp without sacrificing daily drivability. Stronger builds support 500, 600, or more — within the rating of the engine you choose. Don't push an engine past its rating and expect it to last.

How to Choose a Reputable Engine Builder

The builder matters as much as the components inside. A reputable builder brings precision and quality control to the whole process and stands behind the result after the sale.

Look for Proven Expertise and Track Record

Experience is non-negotiable. You want a builder who specializes in Subarus and shows their work. Crawford is the only aftermarket manufacturer ever factory-backed by Subaru of America. Hold any builder to that standard.

The Importance of In-House Machining and Assembly

A builder who controls the process from start to finish controls quality. With machining and assembly in-house, there's no miscommunication between shops and no varying standards — every component is matched and every tolerance met. It also allows real customization: at Crawford, each long block is built to your order and your performance goals.

Why a Strong Warranty Matters

A warranty reflects a builder's confidence in their materials, craftsmanship, and testing. Every Crawford long block carries a 1-year / 12,000-mile warranty. A weak warranty — or none — is a red flag. Ask about the conditions before you buy, not after something goes wrong. Ours are stated plainly: break the engine in as specified, and complete the first oil analysis.

Budgeting for Your Build: The Real Cost of an EJ25 Long Block

The price of the long block is the starting point, not the total. A complete budget covers the engine, the supporting modifications, installation, and a professional tune. Plan the whole project up front and you avoid costly surprises.

Entry-Level Builds

An entry-level build fixes the stock EJ25's weak points and provides a solid foundation for more power. Expect a built engine with forged pistons to reliably handle around 400 horsepower at the wheels. A quality, street-focused long block typically starts around $8,000 — the popular choice for WRX owners who want a real performance jump without giving up daily usability.

Mid-Range and High-Output Builds

Bigger goals cost more. A long block rated for 550 horsepower runs around $10,000. Higher-output builds run closer to $13,000. The higher price reflects stronger connecting rods, a more robust build specification, and the additional machining required to support that power safely. These are the builds for dedicated track cars and high-performance STI projects, priced as one MSRP — no discount framing, no games.

Shipping, Installation, and Labor

One cost you don't carry on the engine itself: Crawford-built long blocks ship free. That is deliberate, and distinct from OEM motors, which pay shipping.

Professional installation is a must and can cost several thousand dollars depending on labor rates. The engine also requires supporting modifications — a stronger fuel pump, larger injectors, a bigger turbo, an upgraded clutch, a better cooling system — plus a professional tune. Add it up and supporting costs can equal or exceed the price of the long block itself.

Essential Supporting Mods for Your Built Engine

The long block is the centerpiece. The systems around it decide whether you get the reliable power you paid for.

Fuel System Upgrades

More power needs more fuel, and the stock system often can't keep up. Run lean and you get excessive heat and, potentially, catastrophic failure. Upgrade to a higher-flow fuel pump and larger injectors, with fuel lines and rails as the build requires. Sizing matters — the fuel system is what your tuner works from.

Turbo and Boost Management

A built engine handles significantly more boost than a stock one, so pair it with the right turbocharger for your goal — a larger stock-location turbo or a rotated setup. A quality electronic boost controller gives precise control. The hardware is half the story: a professional custom tune makes the turbo operate efficiently and safely within your engine's limits. Crawford does not sell tuning. Budget for a professional tuner as part of the build.

Oiling System Upgrades

The flat-four layout presents unique oiling challenges, especially under the G-forces of hard cornering. An AOS is non-negotiable on a built engine: it keeps oil out of the intake, protects your fuel's octane rating, and removes a common cause of ringland failure. An upgraded oil pickup and a baffled oil pan prevent oil starvation during aggressive driving.

Cooling System Upgrades

More power generates more heat. The stock radiator can be overwhelmed, especially on track days or in warm climates. An upgraded aluminum radiator — larger core, more efficient design — holds stable operating temperatures and protects the engine from heat-related stress.

Clutch and Drivetrain Reinforcements

Power is useless if it can't reach the ground. The stock clutch is designed for stock torque and will slip or fail against a built motor's output. Install a performance clutch and flywheel rated for your power goals. At higher power levels, reinforce axles and driveshafts as well.

Break-In and Maintenance

A built engine demands more attention than a stock one, not less. Follow the break-in procedure exactly — it is a condition of the warranty:

• Change the oil at 500 miles and again at 1,500 miles.
• Keep engine speed between 2,000 and 4,500 RPM, varied.
• No sustained cruising and no full-throttle pulls.
• Do not exceed 80% of target boost until break-in is complete.
• Complete the first oil analysis. It is mandatory, and it is a warranty condition.

After break-in, keep a stricter schedule than stock: regular oil changes with high-quality synthetic oil, attention to your gauges, and immediate action on unusual sounds or behavior.

Debunking Myths About Built EJ25 Engines

Myth: All Built Long Blocks Are the Same

They are not, and this is the most dangerous myth here. "Built" only means stock components were replaced with aftermarket parts. The quality of those parts, the precision of the machine work, and the skill of the assembler decide reliability. A poorly assembled engine with cheap parts can be less reliable than a healthy stock motor.

Myth: More Power Always Means Better Reliability

A built engine raises the power ceiling; it doesn't remove it. A stock EJ25 gets risky beyond about 350 whp, and a built engine is rated for a specific level for a reason. Pushing a 500-horsepower build to 700 horsepower will compromise its longevity. Reliability is a solid engine, kept inside its rating, with a conservative professional tune.

Myth: Forged Internals Are Indestructible

Forged pistons and rods are a massive improvement over stock cast components, and they're essential for reliable power over 400 horsepower. They are not indestructible. Severe detonation from a bad tune, oil starvation, or extreme overheating can damage a forged piston just as it damages a cast one. Forged parts give you a much higher tolerance for stress — not immunity from it.

Myth: Built Engines Don't Need Maintenance

The opposite is true. Tighter tolerances and higher stresses mean you can't afford to neglect a built engine.

Is a Built Long Block the Right Move for Your Subaru?

A built long block is for the owner who has felt the stock EJ25's limits, or who wants power with the strength in reserve to hold it.

Defining Your Goal: Street, Track, or Both?

Start with the endgame. A street car wants reliability and a broad powerband. A track build emphasizes power output and surviving constant high-RPM use. Your answer shapes every decision, from components to the final tune.

Best Subaru Models for an Engine Build (2002–Present)

The WRX and STI are the natural candidates — a built block is the key to pushing safely past factory limits. A built engine also transforms a Forester XT or Legacy GT into a genuine sleeper, and off-road models benefit too: reliable power for trails and heavy loads.

Matching the Build to Your Driving Style

A daily driver is well served by a reliable 400 whp from a forged-piston build: a huge gain that stays behaved in traffic. Bigger track numbers mean stronger rods and reinforced components, supporting 500, 600, or more horsepower — up to the rating of the engine you select. Build for the power you'll actually use.

Related Articles

• The Ultimate Built Subaru EJ25 Long Block Guide
• Expert Subaru Solutions: How to Fix EJ25 Short Block Issues
• Built Subaru Engines and Racing
• Best Engine Mods for the STI
• EJ257 Built for Boost

Frequently Asked Questions

Why can't I just put a bigger turbo on my stock EJ25 engine? A bigger turbo adds power, but the stock internals — particularly the cast pistons — aren't designed for the extra stress. Increased cylinder pressure makes them vulnerable to ringland failure. A built engine replaces those weak points with forged parts that can safely manage the power.

What is the main difference between a short block and a long block? A short block is the bottom half: the block with pistons, rods, and crankshaft assembled. A long block adds the cylinder heads, camshafts, and valvetrain. A long block ensures the top and bottom ends are professionally matched and assembled, which simplifies installation.

Is a built engine reliable enough for a daily driver? Yes. A professionally built engine is often more reliable than a stock engine pushed beyond its limits. The point of the build is power made safely and sustainably — the factory weak points are replaced, with strength in reserve.

What other costs should I budget for besides the long block itself? Budget for a higher-flow fuel pump, larger injectors, a performance clutch, and an upgraded radiator, plus professional installation and a custom tune. Rule of thumb: supporting costs run similar to the price of the long block.

After my built engine is installed, what is the most important thing I can do to protect it? Follow the break-in procedure and the maintenance schedule, and get a professional tune. Break-in: oil changes at 500 and 1,500 miles, engine speed between 2,000 and 4,500 RPM and varied, no sustained cruising or full-throttle pulls, no more than 80% of target boost until break-in is complete. The first oil analysis is mandatory — it's a warranty condition. Questions on a build: (855) 677-8243.

Oiling hardware for the build

Crawford stocks the Killer B Motorsport oiling parts these builds call for: the EJ25 Ultimate Oil Pickup at $149.00, the EJ20/EJ25 Performance Baffle at $87.00 — or the pickup and baffle combo at $219.00 — and the High Performance Cast Oil Pan at $549.00. The full line is in the Killer B Motorsport collection.

Related reading: EJ25 Long Block: A Guide to Power & Reliability.