FA20 Long Block: The Definitive Buyer's Guide

October 29, 2026

A long block is the short block plus the top end: cylinder heads, camshafts, and valvetrain, assembled and timed by the builder. You bolt on your intake manifold, turbo, and accessories. If your heads are good and you have a machine shop you trust, a short block can be enough. If the heads are hurt — or you don't want two shops blaming each other when something goes wrong — buy the long block. One builder owns the whole core, and it arrives assembled instead of in boxes. That cuts downtime and takes assembly error off the table.

Which FA20 you have

Subaru built the FA20 two ways. Know which one is in your car before you order anything.

The FA20F is the turbocharged, direct-injected version. It's in the 2015–2021 WRX and the 2014–2018 Forester XT. It was built to take boost, and it's the engine Crawford builds long blocks around.

The FA20D is the naturally aspirated version in the 2012–2020 BRZ, FR-S, and 86. It runs direct and port injection and revs. Different engine, different build path.

What's inside

A stock FA20 runs cast pistons and cast connecting rods. Fine at stock power. They are also the first parts to fail when power goes up. A bent or broken rod is rod knock on its way through the case.

A built long block replaces them: CrawfordSPEC JE forged pistons, forged connecting rods, performance bearings, upgraded head studs. Forging makes a denser, stronger part than casting. It takes cylinder pressure that cast parts can't. The heads are built as part of the same assembly — porting and valvetrain work where the build calls for it — not an unknown you bolt on and hope for the best.

Compression ratio is set by the piston, and it has to match your turbo and your fuel. A build running E85 can support a higher compression ratio than one on pump gas. There is no universal right answer. There is a right answer for your combination.

The stock FA20 case is an open-deck design: the tops of the cylinder walls are not fully supported. At high power, cylinder-wall support matters. What doesn't change at Crawford is the starting point — every build begins with a brand-new OEM block. No used cases. No customer cores.

Why not just push the stock engine

You can push a stock FA20 to about 350–400 horsepower. Past that, you're spending borrowed time on cast internals, and the failure is rarely graceful.

A built long block seals better, too. Pistons and rings fit during a proper build cut blow-by, which is where much of the stock engine's oil consumption comes from. Oil vapor in the intake is its own problem — it's why Crawford developed the original closed-loop air oil separator. An AOS belongs on any built FA20: it returns separated oil to the engine instead of venting it or filling a can you have to empty.

A built engine is not a track-only proposition, either. A professionally built and properly tuned long block is more reliable as a daily driver than a stock engine pushed past its limits on bolt-ons. The stronger parts handle stress with margin to spare.

Crawford's FA20 long blocks

Crawford sells the FA20 long block in two lanes: built, and BTO — Better Than Original. Crawford's FA20 DIT short block is rated at 660 hp, and the long block is that bottom end with the top end built and installed. A built FA20 handles over 600 horsepower; the number you actually make depends on the turbo, fuel system, and tune behind it. The engine is the foundation. It is not the whole build.

Every Crawford motor starts from a brand-new OEM block. No core is required or needed. There is no core charge and no deposit to get back later. Crawford-built long blocks ship free.

What it costs

A professionally built FA20 long block runs from $9,000 to over $19,000. Internals, head work, and machine work set where a build lands in that range. That's the engine. It is not the total.

Budget for the rest of the system: a larger turbo, higher-flow injectors, a fuel pump that keeps up, a better radiator, an oil cooler, an AOS, shipping on anything that doesn't ship free, professional installation, and a tune. Starve a built engine of fuel under boost and forged parts won't save it. A swap to a different engine platform is worse, not better — custom mounts, wiring, and fabrication to solve problems the FA20 doesn't have.

Choosing a builder

Buy the builder before you buy the parts list. The questions that matter:

Is he a Subaru specialist, or a general engine shop? The FA20 has specific oiling and cooling behavior. A specialist knows it because it's all he does.
Will he show you the exact parts list? Forged pistons and rods from named manufacturers, bearings, head studs — in writing. Vague is a red flag.
What's the warranty, and what does keeping it require? See below. Ours is in writing too.
What do his customers say where he can't edit it? Forums, groups, Google — not just his own testimonials.

A custom build, where you pick every component, offers the most control and demands the most knowledge. A pre-configured package puts the matching on the builder. For most owners chasing reliable power, the package is the right call.

Break-in and warranty

Crawford-built engines carry a 1-year / 12,000-mile warranty. Break-in and the first oil analysis are mandatory — they are warranty conditions, not suggestions.

The break-in spec:

Oil changes at 500 and 1,500 miles.
Keep engine speed between 2,000 and 4,500 RPM, and vary it. No sustained cruising. No full-throttle pulls.
Do not exceed 80% of target boost until break-in is complete.
First oil analysis is mandatory.

The oil changes matter because new rings and bearings shed microscopic metal as they seat. Getting that debris out is the point.

A professional tune is not optional. The tune makes the new parts work together — air-fuel ratios right, timing right. A bad tune can kill a good engine, and no warranty covers that.

Two more rules worth following. Watch oil pressure, coolant temperature, and air-fuel ratio on real gauges; the dashboard light warns you after the damage is done. And if the engine you're replacing failed internally, replace the fuel injectors. A failed engine sheds fine metal through the oil and fuel systems. A contaminated injector can stick open and wash a cylinder, or stick closed and lean one out. Either one can destroy a new long block.

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