ATK 388 Short Block SPE3881800 | Dart LS Next 1800HP

ATK Elite Series 388 LS Short Block — SPE3881800

The ATK 388 short block is an Elite Series LS assembly built for boost and nitrous, rated to 1800 horsepower. It uses a Dart LS Next cast iron block rather than a factory casting, which is the difference between a bottom end that survives serious power and one that becomes a core charge.

The ATK 388 short block is exactly that — block, crank, rods, pistons and rings, assembled and balanced. Heads, cam, intake, and accessories are not included.

ATK 388 Short Block Specifications

• Displacement: 388 cubic inches
• Power rating: 1800 HP
• Block: Dart LS Next, cast iron, 4.125″ bore
• Crankshaft: Billet steel, 3.622″ stroke
• Connecting rods: Forged 4340 I-beam
• Pistons: Forged 2618, flat top
• Rings: Pro Seal
• Reluctor: 58x
• Intended use: Boost and nitrous ready
• Manufacturer part number: SPE3881800

Why the Dart LS Next Block Matters

Factory LS blocks are excellent castings, but they were never designed for four-figure power. The common failure is not the block cracking — it is main webbing flex and cylinder wall distortion under sustained boost.

The LS Next casting addresses both with thicker decks, revised water jacketing, and a priority main oiling arrangement. On the ATK 388 short block that means the bottom end holds ring seal at power levels where a stock block loses it.

The ATK 388 short block runs a genuine big bore at 4.125 inches, not an overbored 6.0. Combined with the 3.622-inch stroke, it produces 388 cubic inches with a bore-to-stroke ratio that favours airflow and high-rpm breathing.

Forged Internals, and Why 2618 Pistons

2618 alloy is the low-silicon forging used where detonation resistance matters more than tight cold clearances. It expands more than 4032, so a 2618 build runs looser piston-to-wall clearance and will make more noise cold — that is normal, not a defect.

The trade is worth it under boost. 2618 tolerates heat and abuse that would crack a hypereutectic piston, which is why the ATK 388 short block uses it rather than a cheaper cast option.

Billet steel crankshafts and forged 4340 I-beam rods complete the ATK 388 short block rotating assembly. The whole thing arrives balanced, so you are not paying a machine shop to redo work already done.

What You Still Need to Buy

The ATK 388 short block is a foundation, not a running engine. Budget for cylinder heads, camshaft and valvetrain, intake manifold, oil pan and pickup, timing set, front and rear covers, harmonic balancer, flexplate or flywheel, and a complete gasket set.

For best results: specify the camshaft with your intended boost level and converter already decided. Cam selection on an 1800 HP capable bottom end is where most builds are won or lost, and it is far cheaper to get right before assembly than after.

Not sure what completes your combination? Book a technical consultation before ordering, or submit a quote request for a full package.

Who This Is For

This is a purpose-built race and high-boost bottom end. If you are assembling a turbocharged or supercharged LS for drag racing, a high-horsepower street build, or a dedicated competition car, the ATK 388 short block is sized and specified for it.

If you want a naturally aspirated street engine, this is more block than the application needs. The LS3 415 short block or the LQ4 6.0L short block are the sensible alternatives, and the full short block engines range covers everything between.

Want a larger Dart LS Next assembly? Compare the 427 Dart Race Series short block.

Ordering, Fitment and Support

Confirm your ATK 388 short block application first — LS Next blocks differ from factory castings in accessory mounting and oiling, and not every OEM part carries over. Run a compatibility check or send a part request if you need a variant not listed.

We also offer engine installation and custom build services if you would rather have the complete engine delivered assembled. Review warranty information and shipping information before ordering — short blocks ship freight, not parcel. Manufacturer specifications are published by ATK High Performance Engines.