Engine Blocks & Long Blocks

Choosing the Right Block

Performance engine blocks for LS swaps, and for Ford and Hemi builds, are not interchangeable commodities. The block you choose sets the ceiling for displacement, boost, and longevity. Get the bore, deck height, and material wrong and you're either leaving power on the table or rebuilding sooner than you planned.

Four criteria drive the decision: whether you want a bare block or a long block assembly, cast iron or aluminium, what bore size and deck height you need, and which engine family your swap chassis is built around. Work through them in order and the field narrows quickly.

Long Block vs Bare Block

A long block arrives with the crankshaft, connecting rods, pistons, cylinder heads, and valvetrain already installed. The rotating assembly is balanced, the heads are torqued, and you're adding intake, exhaust, ignition, and ancillaries rather than building from scratch. For a builder who wants to compress the assembly phase or who doesn't have access to an engine stand and a dial bore gauge, a long block is the practical choice.

A bare block gives you a precision casting and nothing else. You specify every internal component, crank stroke, rod ratio, piston compression height, head combination, and you or your engine builder assemble it. That flexibility matters when you're chasing a specific displacement target, running a non-standard bore, or sourcing components from a preferred supplier. Most of the blocks in this collection are bare castings.

Material: Cast Iron vs Aluminium

Cast iron is heavier, cheaper, and more forgiving under heat cycles. The thermal mass helps stabilise combustion temperatures on long pulls, and the material tolerates detonation better before showing damage. For a budget street build or a truck application where weight isn't a concern, cast iron is a sensible choice. The Dart LS Next iron blocks and the Chevrolet Performance LSX castings are both cast iron.

Aluminium saves meaningful weight, typically 40 to 50 lb over a comparable iron block, and dissipates heat faster, which can be an advantage in a tightly packaged engine bay. The trade-off is cost: aluminium aftermarket blocks carry a premium, and they require closer attention to coolant chemistry and head gasket selection to prevent galvanic corrosion. For a swap build where front axle weight matters, or for a track car where every kilogram counts, the aluminium Dart LS Next variants are worth the additional outlay.

On forced induction, both materials can handle serious cylinder pressure if the block is engineered for it. The question is less iron vs aluminium and more whether the casting is designed for boost, four-bolt or cross-bolted main caps, thicker cylinder walls, reinforced oil galleys.

Bore Size and Deck Height

Bore and deck height determine displacement ceiling and stroker compatibility. A 4.000-inch bore with a 9.240-inch deck on a standard LS journal crankshaft produces approximately 364 cubic inches (6.0 litres). Stepping up to a 4.125-inch bore with the same deck and a stroker crank opens the door to 427 or larger. The 9.450-inch tall-deck iron block takes that further still, accommodating longer-stroke assemblies that wouldn't clear the pan rails on a standard-deck block.

For forced-induction LS builds, bore size interacts with rod-to-stroke ratio and piston design. A larger bore gives more swept area but requires careful matching with the head's quench and combustion chamber geometry. If you're planning boost above 15 psi, the block's bore needs to be matched to forged pistons with appropriate ring packs, not the stock cast items.

Deck height also determines which cylinder heads will seal correctly. All standard LS Next 9.240-inch deck blocks accept standard LS-generation head gaskets. The 9.450-inch tall-deck variant requires tall-deck-specific gaskets and intake manifolds. Confirm before ordering heads.

Block Family and Platform Fitment

The LS and LT families dominate this collection, and with good reason, they fit more swap applications than any other American V8. The engine mounts, transmission bellhousing patterns, and oil pan configurations are well-documented for almost every common UK swap chassis. Dart's LS Next series is dimensionally compatible with the standard Gen III/IV LS envelope: same bellhousing bolt pattern, same motor mount ears, same oil pan rail geometry.

The Ford Performance Godzilla block (7.3 V8, M-6010-SD73) is a separate ecosystem entirely. It serves Ford builders, classic Escorts, Transits with a sense of humour, or American muscle projects that stay in the Blue Oval family. It does not share bellhousing or accessory patterns with the GM LS family.

The Dart Gen III Hemi VVT block serves Mopar builds. The 4.090-inch bore and 9.285-inch deck height accommodate large-displacement stroker assemblies for Hemi swaps, and the VVT-compatible architecture keeps options open for variable-valve-timing head combinations.

Where the Criteria Conflict

The decision points pull against each other in a few ways worth knowing upfront.

A long block saves assembly time but removes most of the customisation decisions that a bare block leaves open. If you want a specific camshaft, a particular rod ratio, or a head combination that doesn't match what the long block ships with, you're pulling it apart before it goes in the car. Bare blocks take longer but they're built to your specification.

Aluminium blocks cost more to buy and more to repair if something goes wrong. A cracked iron block can often be sleeved or welded; an aluminium casting with a compromised bore is typically scrap. Budget accordingly.

Stroker-compatible blocks, those with taller decks or relieved skirts, cost more than standard-deck versions. If your current build plan calls for a 383 or a 408, the additional outlay on a stroker-friendly block is worthwhile. If you're building a naturally aspirated 364 that will stay there, a standard 9.240-inch deck block with a 4.000-inch bore is the correct choice and you're not paying for headroom you won't use.

Which Block to Choose

Street LS swap on a budget, naturally aspirated: a Dart LS Next iron block at 4.000-inch bore and 9.240-inch deck gives you a proven aftermarket casting with standard LS fitment. Pair it with a factory-spec crank and a set of hypereutectic or forged pistons depending on compression target.

Forced-induction LS build, street or track: move to a Dart SHP (Super High Performance) block. The additional reinforcement, thicker main webs, four-bolt mains with ARP hardware, is there for a reason. The SHP designation is not marketing; it reflects a different casting specification.

Weight-sensitive street or track build: aluminium Dart LS Next variants shave weight without sacrificing the aftermarket-engineered wall thickness and main cap architecture that bare OEM blocks lack.

Factory-reliability LT build: the Chevrolet Performance LT1/LT4 replacement block is the right tool. OEM dimensional tolerances, no custom machine work required, and it accepts standard LT-generation components without modification.

Ford or Mopar project: the Ford Performance Godzilla block and the Dart Gen III Hemi block are their respective platform choices. Neither is a substitute for the other, and neither fits an LS swap chassis.

Top Picks

Dart SHP LS Next Pro Block, 9.240-inch deck, 4.000-inch bore, ARP main studs

The SHP designation indicates a higher-specification casting than the standard LS Next: reinforced main webs, four-bolt main caps, and ARP main studs already fitted. The 9.240-inch deck and 4.000-inch bore sit in the standard LS envelope, which means it drops into any chassis where a Gen III LS would go. This is the block for a forced-induction LS build, street or strip, where you want to build the rotating assembly to your own spec. Not the cheapest entry point, but the engineering justifies it.

Dart LS Next Aluminium Block, 4.000-inch bore, skirted (31947111)

Aluminium construction, standard 9.240-inch deck, skirted design. Lighter than the iron equivalent and packaged cleanly for engine-bay fitment. Works with standard LS crankshaft and connecting rod combinations up to mild stroker specifications. A sensible choice for a naturally aspirated or lightly boosted street build where front axle weight matters. Budget more carefully for head gaskets and coolant, aluminium requires closer attention than iron.

Chevrolet Performance LT1/LT4 Engine Block

Factory OEM replacement casting from Chevrolet Performance, covering LT1 and LT4 applications. Accepts standard LT-generation components without modification. The right choice for a builder restoring or replacing an existing LT-family engine rather than building a custom stroker. OEM dimensional control means no surprises when you start fitting heads and mains. Not the block to choose if you're planning to depart significantly from factory displacement or boost targets.

Ford Performance Godzilla Engine Block (M-6010-SD73)

Ford's 7.3-litre V8 block in performance-spec casting. Separate ecosystem from the GM LS family, different bellhousing pattern, different accessory architecture, different head bolt pattern. For Ford builders who want serious displacement without leaving the Blue Oval, this is the block. Pair it with Ford Performance rotating assembly and cylinder head components. Check your swap chassis for clearance; the 7.3 is a large engine by modern standards.

Dart Gen III Hemi VVT Engine Block, 4.090-inch bore, 9.285-inch deck

For Hemi swap builds. The 4.090-inch bore and 9.285-inch deck height accommodate large-displacement stroker assemblies, and the VVT-compatible architecture preserves the option of variable-valve-timing heads. The Hemi block pattern does not cross over to LS or Ford applications. If your project runs Mopar, this is the aftermarket casting to build around.

FAQ

What's the difference between a long block and a bare block?

A long block includes the crankshaft, connecting rods, pistons, cylinder heads, and valvetrain pre-installed as a balanced assembly. You add the intake, exhaust, ignition system, and ancillaries. A bare block is a precision casting only, no rotating assembly, no heads. Bare blocks give you full control over every internal specification; long blocks compress the build timeline at the cost of customisation flexibility.

Will a Dart LS Next block fit my LS swap chassis?

Yes, provided the chassis is set up for a standard Gen III or Gen IV LS. Dart LS Next blocks maintain the standard LS bellhousing bolt pattern, motor mount ear positions, and oil pan rail geometry. If your swap kit was designed around a production LS engine, the LS Next drops in using the same mounts and transmission. Confirm the oil pan configuration for your specific chassis before ordering, front-sump and rear-sump pans are not interchangeable.

Can I use an aluminium block on a forced-induction build?

Yes, provided the casting is engineered for boost. The deciding factor is not material, it's whether the block has adequate main cap clamping, cylinder wall thickness, and oiling provision for the power level you're targeting. The Dart SHP LS Next blocks, available in both iron and aluminium, are specifically designed for high-horsepower and forced-induction applications. Standard OEM aluminium castings are a different matter; their wall thickness and main web design were not specified for sustained high-boost cylinder pressures.

What do bore size and deck height actually determine?

Bore size is the cylinder diameter; deck height is the distance from the crankshaft centreline to the block deck surface. Together they define the maximum displacement the block can produce for a given crankshaft stroke. A larger bore increases swept area. A taller deck allows a longer stroke without the piston crowning above the deck or the connecting rod fouling the pan rail. If you're building a stroker, confirm that your chosen crank stroke, rod length, and piston compression height work together within the block's deck height.

Are these blocks pre-honed or do they need machine work before assembly?

It varies by part number. Some Chevrolet Performance LSX castings are production-finished and honed to a specific bore diameter, ready for piston fitting after a light plateau hone. Most Dart blocks are supplied as raw or semi-finished castings requiring final bore and hone to the piston manufacturer's specified clearance. Check the product specification before sending to your machine shop, ordering a block that's already at final bore diameter and then boring it further is not recoverable.

Can I run a stroker crank in a standard 9.240-inch deck block?

Depends on the stroke. A 4-inch stroke in a standard 9.240-inch deck LS block works with appropriate rod length and piston compression height. A 4.125-inch stroke at the same deck height requires careful checking of rod-to-wall clearance and piston-to-head clearance. Longer strokes, typically anything beyond 4.125 inches in an LS, generally benefit from a taller deck. The Dart LS Next 9.450-inch tall-deck iron block exists for this reason. Establish your displacement target first, then select deck height to suit the stroke, not the other way around.