FA24 Engine Replacement Options

Hopefully you enjoy your FA24 for many thousands of miles (or kilometers). However, if you do find yourself needing to replace your engine—or you just want to be prepared—this post covers engine replacement options for the GR86/BRZ (Gen 2).

In short, your options are to buy one of the following:

1. New short block from Subaru/Toyota (and any other damaged components which require replacing)
2. New “Partial Engine Assembly” from Subaru/Toyota
3. New “Complete Engine Assembly” from Subaru/Toyota
4. New built engine from a performance shop
5. Used engine typically from a totaled car (ideally from a rear-end accident)

I went through this process when I replaced a blown engine in November 2023 and decided to get a Complete Engine Assembly from Subaru. However, the Partial Engine Assembly did not exist at that time. If it did exist then, I probably would have gone with that option.

I’ll walk through each of these options and their tradeoffs so you can make your own (hopefully theoretical) decision.

Short Block

Part	Subaru P/N	Lowest Seen Price
Short Block (All models)	10103AD100	$1,823

A short block is the “bottom end” of the engine. It is composed of the engine block (two halves with a seam down the center, in our case), plus the pistons, connecting rods, crankshaft, and all main and connecting rod bearings. All these parts come already assembled, so you don’t need to worry about things like bearing clearances.

This option has the lowest up-front price, but it comes with a number of hidden costs and risk. If you are rebuilding your engine before a failure has occurred this is a great option.

Once you’ve suffered a failure, however, it is likely that damage has been done to other parts of the engine. For example, a connecting rod bearing failure could cause a piston to travel up in the cylinder further than it was designed to do. This would cause it to contact with the valves, introducing damage to the valvetrain and potentially distributing shrapnel throughout the engine. This metal debris would then cause damage to the oil pump.

Even with a new short block, you may end up needing to replace heads, camshafts, the timing cover assembly and oil pump, etc. Even worse, you could miss a part you should have replaced and that could cause a failure in your rebuilt engine.

There’s also a risk for error in assembly leading to a future failure. You have to correctly reassemble everything, correctly seal the many mating surfaces, and correctly time the engine. All of this is possible to do, but it is highly dependent on the skill of the person doing the work. Even if you pay someone else to do it, you rely on their guarantee, if any exists.

Let’s just say: if you aren’t already confident in rebuilding from a short block, you should skip to the next options.

Partial Engine Assembly

Part	Subaru P/N	Lowest Seen Price
Partial Engine Assembly (MT)	10118AA990	$5,677
Partial Engine Assembly (AT)	10118AB001	$5,677

This is a relatively new option and is likely the best option for most FA24 failures.

This was not available when I replaced my engine, so I haven’t seen the assembly for myself. In order to find out more info about exactly what this contains, I went to my local Subaru parts counter and asked them if they had a part list or could otherwise tell me what it includes. The following image is the sum total of what they are able to see in their system:

Assuming this image is accurate (and I believe it is), the Partial Engine Assembly should be a traditional long block, with water pump, crankshaft pulley, oil pan, oil filter, spark plugs, and flywheel.

This seems to be a good option because it is substantially cheaper than the Complete Engine Assembly and, if you’re replacing an existing FA24, you already have all the other accessories you need. The risk involved in swapping over these parts is very low compared to a rebuild.

Complete Engine Assembly

Part	Subaru P/N	Lowest Seen Price
Complete Engine Assembly (MT)	10100CE990	$7,312
Complete Engine Assembly (AT)	10100CF010	$6,940

Contrary to the comparison picture above, this part is not just the outline of an engine. It contains a plug-and-play FA24, fully dressed with all necessary accessories, harnesses, sensors, etc.

It contains the clutch and pressure plate (for manual transmission), accessory belt and all pulleys, alternator, AC pump, ignition coils, fuel rails and injectors, intake manifold, and throttle body.

While this is convenient, you should decide whether it is worth it to pay more for this option, or get the Partial Engine and transfer over these parts. I haven’t priced out these individual parts, but it might actually be reasonable to get the Complete Engine and either keep the duplicate parts as spares or sell them off to lower the effective price.

The risk for this option is approaching zero.

New Built Engine

Another option is to get a “built” engine while you are swapping the engine anyway. Performance shops will sometimes offer a built short block, but others may offer a built long block. The same tradeoffs as described above exist when deciding between a short block or a long block.

Because the FA24 is still relatively new, there don’t seem to be many fully assembled built engines available on the market, but this is likely to change over time.

If you’re happy with stock power, I’d recommend sticking to the Subaru options above. Otherwise, do your homework.

Used Engine

For around $5,000 you can get an engine that has been removed from a crashed GR86/BRZ. In my opinion, this is not enough of a discount to the Partial Engine to make it worthwhile.

The risks here are numerous:

• Previous mechanical overrev if it came from a manual transmission car
• Bearing damage due to running low oil levels or oil starvation
• Improper break-in

For a stout engine like a Honda K-series, where used engines are as low as $1,000, these risks make a lot more sense. However, for only a few hundred dollars less than a Partial Engine—and for a less robust engine—I think this risk is too high.

Future Changes

Over time, I don’t expect the official Subaru options to change much in price. A short block assembly from Subaru for an FA20 for the previous generation 86/BRZ still costs around $2,000. So, it’s likely that the math here won’t change much until the FA24 is out of production. (Can I interest anyone in a Toyota powertrain for Gen 3?)

At that point, Subaru will likely stop offering the Complete Engine Assembly part altogether, but they should still offer the Partial Engine Assembly.

Conclusion

I think the best option for most people looking to replace a failed engine (and assuming you aren’t covered under warranty—separate topic) is likely to be the Partial Engine Assembly.

A Complete Engine Assembly (plus selling off duplicate parts) may be pretty comparable in terms of price and requires less labor. If you are paying for labor, this might tilt the balance in favor of buying a Complete Engine.

Short Blocks offer some up-front cost savings in exchange for much more labor and much higher risk.

I’d avoid used engines unless you know the history of the engine and the savings justifies the risk.

Do you have more info on these options? Can you confirm the details I found on the Partial Engine option? Let me know (contact info below)!