Diesel Power Holland completed a full Caterpillar 3412 longblock rebuild for marine use, overhauled in-house at our Moerdijk workshop to exact Caterpillar standards and available for immediate worldwide delivery. A longblock rebuild replaces every core internal component of the engine, making it the closest equivalent to a new engine short of purchasing a factory-new unit. For operators of 3412-powered vessels facing a major overhaul decision, a rebuilt longblock from Diesel Power Holland is the fastest and most cost-effective path back to full power.

What Is a Caterpillar 3412 Longblock?

A longblock is a rebuilt engine assembly that includes all core internal components, the cylinder block, crankshaft, cylinder heads, pistons, camshafts, bearings, and valve train, fully assembled and ready for installation. It does not include external accessories such as the turbocharger, exhaust manifolds, injection pump, or cooling system components, which are typically reused from the original engine or sourced separately.

A longblock rebuild is the preferred overhaul solution when the internal engine components are worn beyond acceptable limits but the external ancillaries are still serviceable. It delivers effectively new engine internals in a faster and more cost-efficient format than a complete engine replacement.

The Caterpillar 3412 is a 27.0-litre, V12 diesel engine widely used in marine propulsion, generator drive, and heavy industrial applications. Its V12 configuration delivers high power output and smooth torque characteristics suited to demanding continuous-duty marine environments.

Caterpillar 3412 Longblock: Components included in the rebuild

The Diesel Power Holland 3412 longblock rebuild covers all critical internal assemblies:

• Cylinder block group
• Crankshaft
• Cylinder packs and cylinder heads
• Piston cooling jets
• Camshafts
• New bearings (main, big-end, and camshaft)
• Powertrain distribution — rear and front gear sets
• Flywheel and oil pump
• Injectors and valve train
• Oil and fuel filter housings
• Finished in CAT yellow

Every component is inspected, measured, and either reconditioned or replaced before assembly. The longblock is built to Caterpillar’s own standards and procedures, the same benchmark used in factory production.

Longblock vs. Full Engine rebuild: What Is the Difference?

Understanding the difference between a longblock and a full engine rebuild helps operators make the right overhaul decision:

A longblock covers all internal engine components from the block up — crankshaft, pistons, heads, camshafts, bearings, and gear drives. External components (turbocharger, injection pump, coolers, manifolds) are not included and are reused or replaced separately.

A full engine rebuild covers the complete engine including all ancillaries: turbocharger, fuel system, cooling components, starting system, and instrument panel, resulting in a complete, ready-to-run engine package.

For marine operators whose 3412 requires a major internal overhaul but has serviceable ancillaries, a longblock rebuild is the most efficient solution: shorter lead time, lower cost, and full compatibility with existing vessel systems.

Why the Caterpillar 3412 is used in marine applications

The 3412 remains a widely deployed marine engine because of its 27-litre V12 displacement, which delivers high sustained torque at relatively low RPM, a characteristic critical for propulsion and generator drive applications where load is continuous and consistent. The engine’s long production run (spanning several decades) means that parts availability, rebuild expertise, and field experience are all well-established globally.

The 3412 series was produced in several variants including the naturally aspirated 3412, the turbocharged 3412T, and the turbocharged-aftercooled 3412E — each with different power ratings and application profiles. Diesel Power Holland has experience rebuilding longblocks across the full 3412 family.

FAQ: Caterpillar 3412 Longblock Rebuild

What is included in a Caterpillar 3412 longblock rebuild? A 3412 longblock rebuild includes: cylinder block, crankshaft, cylinder packs and heads, piston cooling jets, camshafts, new bearings, front and rear gear sets, flywheel, oil pump, injectors, valve train, and oil and fuel filter housings, all assembled to Caterpillar factory specifications.

What is not included in a longblock? A longblock does not include the turbocharger(s), exhaust manifolds, fuel injection pump, heat exchangers, coolers, starting motor, alternator, or instrument panel. These components are typically transferred from the original engine or sourced separately.

How does a 3412 longblock differ from a shortblock? A shortblock covers only the lower engine assembly — block, crankshaft, pistons, and liners — without the cylinder heads, camshafts, or valve train. A longblock is a more complete assembly that includes all of these upper engine components, requiring less additional work at installation.

Is a rebuilt Caterpillar 3412 longblock as reliable as a new engine? When rebuilt to Caterpillar factory standards using OEM-quality components, a longblock delivers the same internal tolerances and performance characteristics as a new engine. Diesel Power Holland rebuilds all 3412 longblocks to the procedures and specifications defined by Caterpillar.

How quickly can Diesel Power Holland deliver a rebuilt 3412 longblock? The 3412 longblock is available for immediate delivery from our warehouse in Moerdijk, the Netherlands. Shipping is available worldwide with full export documentation and logistics support.

Can Diesel Power Holland rebuild my existing 3412 engine as a longblock? Yes. We accept customer cores for longblock rebuild at our workshop. Contact us with your engine’s serial number and prefix to receive a rebuild assessment and quote.

Need a Caterpillar 3412 Longblock?

Whether you need a rebuilt 3412 longblock from stock or want to send in your own core engine for overhaul, Diesel Power Holland is your specialist. With over 1,000,000 Caterpillar parts in stock and 45+ years of experience in Caterpillar marine and industrial engines, we deliver the right solution — fast.

Contact us for availability, pricing, and technical support on your 3412 longblock project.