Which Is Right for Your Subaru Build?
When planning a Subaru engine build or replacement, one of the first big decisions is whether to go with a short block or a long block. Both options have their place, and the right choice depends on your goals, budget, and how much work you want to take on.
If you are exploring engine options, you can browse the full Subaru Engine Components category to see what fits your build.
This guide breaks down the differences in simple terms so you can choose the setup that makes the most sense for your build.
What Is a Short Block?
A short block is the bottom end of the engine. It typically includes the engine block, crankshaft, rods, pistons, and bearings. It does not include the cylinder heads, cams, valvetrain, or timing components.
Short blocks are a popular choice for Subaru owners who already have good cylinder heads or want more control over their build. You can view available options here: Subaru Short Blocks.
When a Short Block Makes Sense
A short block is usually the right option if:
- Your cylinder heads are in good condition or already built
- You want to reuse or upgrade specific top-end components
- You are doing a performance build with custom parts
- You are working with a tighter budget compared to a full engine
Many performance builds use reinforced internals from brands like IAG Performance, especially for FA20 and EJ platforms targeting higher power levels.
What Is a Long Block?
A long block is a more complete engine assembly. It includes the short block plus cylinder heads, cams, valvetrain, and often timing components. In many cases, it is close to a drop-in solution.
For Subaru owners who want a simpler path, long blocks remove a lot of the guesswork. Explore current options here: Subaru Long Blocks.
When a Long Block Makes Sense
A long block is usually the better choice if:
- Your original engine failed and damaged the heads
- You want a faster, more straightforward install
- You want a matched, professionally assembled setup
- You prefer reliability and convenience over customization
Long blocks are especially common for daily drivers, street builds, or situations where downtime needs to be minimized.
Cost vs Labor Considerations
At first glance, a short block is cheaper. However, labor and additional parts can close that gap quickly.
With a short block, you may need head inspection or machine work, new valves or seals, additional assembly labor, and extra gaskets and hardware. Supporting upgrades such as a stronger clutch from Competition Clutch or ACT are also common once power increases.
A long block typically costs more upfront, but often reduces labor time and unexpected expenses during the build.
Performance and Reliability Differences
Both short blocks and long blocks can support serious power when properly built. The difference is less about performance potential and more about execution.
A well-matched long block offers consistency and reliability because all components are designed to work together. A short block build can perform just as well, but it depends heavily on part selection and assembly quality.
Engine builds are often paired with proper ECU calibration using systems found in the EFI Tuning category to ensure safe air-fuel ratios and boost control.
Real World Examples Using IAG Blocks
Many Subaru owners choose IAG Performance components because they offer clearly defined power levels and use cases, which makes planning a build much easier.
For example, if you are rebuilding a daily driven WRX with mild bolt-ons, an IAG FA20 short block allows you to retain your factory cylinder heads while upgrading the internals for improved reliability.
If you are dealing with a full engine failure or planning a more complete refresh, an IAG long block provides a fully assembled solution where all components are matched and professionally built, reducing installation time and uncertainty.
Frequently Asked Questions
Can I reuse my cylinder heads with a short block?
Yes, as long as the heads are in good condition. In many cases, they should be inspected or refreshed before installation to ensure proper sealing and long-term reliability.
Is a long block worth the extra cost?
For many builds, yes. A long block reduces labor time, removes compatibility concerns, and is often the better choice when the original engine suffered significant damage.
Do short blocks and long blocks support the same power levels?
They can. Power capability depends more on the internal components and overall build quality than whether the engine is a short block or long block.
Which option is better for a daily driven Subaru?
Both can work well. A long block is usually preferred for simplicity and reliability, while a short block is ideal if you already have good heads and want more customization.
Need Help Choosing the Right Engine Setup?
If you are planning an engine rebuild or upgrade and are unsure whether a short block or long block is the right choice, Wrench Masters can help.
Reach out with your vehicle details, goals, and power targets, and we can help point you toward the best solution for your Subaru build.