Long Block vs Short Block Engines (Full Comparison Guide)

Long Block vs Short Block: Several Differences Every Engine Buyer Must Know

When an engine fails, one of the decisions you’ll face is choosing between a long block vs short block. At first glance, the difference between long block and short block engines may seem technical or minor. However, choosing the wrong option can cost you thousands of dollars, weeks of downtime, and a lot of frustration. 

Understanding the difference between these two engine assembly types is crucial, not just for mechanics, but for operators, fleet managers, and business owners in the heavy equipment industry. In this article, we’ll break down everything you need to know about long blocks vs. short blocks and how to make the right call when it comes to deciding whether you should rebuild or replace an engine. 

What Is an Engine Block?

Before comparing a short vs long block, it helps to understand what an engine block (bare) actually is. This is also known as the cylinder block. 

The engine block is the foundation of any diesel engine. It houses the cylinders, crankshaft, and internal oil and coolant passages. 

In heavy equipment machinery, this block must withstand massive stress. Think of a Bobcat skid steer pushing several tons of earth, or a Kubota tractor running all day in harsh conditions, its block must handle extreme heat, pressure, and vibration consistently. When that block gets damaged or when internal components wear out (a cracked block, spun bearing, dropped valve, blown head gasket), the block assembly is often the part that must be replaced. Oftentimes, it’s  more economical and efficient to replace the engine in part or whole, and that’s where short and long blocks come into play.

What Is a Short Block Engine?

A short block is the lower part of the engine assembly, containing only the core rotating components like the crankshaft, pistons, and rods. It’s called “short” because it excludes all the top-end components such as anything related to airflow, fuel delivery, or valve control. 

But don’t let the name fool you. Just because it’s missing the upper components doesn’t mean it’s insignificant. This foundational assembly plays a major role in your engine’s overall performance.

A typical short block includes:

• Engine block
• Crankshaft
• Pistons
• Connecting rods
• Main bearings
• Connecting rod bearings
• Camshaft with gear, washer and bolts
• Other bearings and plugs

Short blocks typically do not include the cylinder head, valve train, oil pump, timing components and in many cases, the camshaft. This is a fundamental difference between short and long blocks. Short blocks require you to reuse or source many additional parts.

When a Short Block Makes Sense

A short block can be the right choice when:

• Only the bottom end of your engine is damaged (e.g., spun bearing, thrown rod)
• Your cylinder head is in excellent condition (e.g., no cracks, valves show no signs of burning, cleanliness, etc)
• Your camshaft and valve train are reusable 
• You have experienced diesel technicians available (this is key)
• You’re rebuilding a rare or discontinued engine
• Budget is your top priority

For example, a customer rebuilding a remanufactured short block for a Doosan D18 diesel engine may choose this route if they’ve already invested heavily in top-end components. However, short blocks are not forgiving. If one reused component fails, you’re right back where you started, so it’s important to be sure you can reuse the above components. 

What Is a Long Block Engine?

A long block includes everything in a short block plus the complete top end of the engine. A long block comes with the cylinder head which is bolted to the short block, and it is nearly a complete engine, minus external accessories like the turbo, starter, or alternator. 

This dramatically reduces complexity and risk during installation.

A long block typically includes:

• Engine block
• Crankshaft
• Pistons, rings, pins and connecting rods
• Camshaft with gear, washer and bolts
• Cylinder head (fully assembled with valves and springs)
• Rocker arms
• Timing components
• Main bearings
• Other bearings and plugs
• We typically include the gasket/overhaul gasket kit and oil pump in our long blocks.

The beauty of a long block is in its plug-and-play nature. You’re saving hours of labor compared to a short block because you’re not rebuilding the top end. This is a huge win if your team is small, you're facing time constraints, or the machine is mission-critical. We actually offer fully assembled long blocks for popular brands, making installation faster and easier, just drop it in and go!

Why Long Blocks Reduce Risk

When comparing short block vs long block, long blocks win on reliability. Since the critical wear components are already matched and assembled, there’s less chance of tolerance stack-up or installation error.

For many engines (e.g. Doosan engines in Bobcat), long blocks are the preferred option because they:

• Reduce install time
• Minimize downtime
• Lower long-term risk

• Simplify logistics

Cost Differences Explained

At face value, a short block is cheaper. However, total cost tells a different story.

Short Block Costs

• Lower upfront price
• High labor hours
• Machine shop expenses
• Risk of reused component failure

Long Block Costs

• Higher upfront price
• Lower labor cost
• Faster return to service
• Fewer surprise repairs

For customers running revenue-generating machines such as excavators, skid steers, or loaders, the long block often ends up being the more economical choice.

Installation Time and Labor Considerations

For most small business owners, time is money, especially when equipment is down.

A short block vs long block comparison often comes down to this:

• Short block installs can take days or weeks
• A short block is best for those who have the tools and expertise to work on their own engines
• Long block installs are often completed in days
• Needing a long block replacement usually means that both the short block and cylinder head are too damaged to be salvaged

On engines like the Doosan D24 engine or Doosan D34 engine, labor savings alone can justify the cost difference.

Remanufactured Short Block vs New Assemblies?

A remanufactured short block can be a viable option when done correctly. However, quality varies widely. Key considerations:

• Was the block magnafluxed?
• Were bearings replaced or reused?
• Are pistons OEM spec?

For high-hour machines, many buyers prefer new short blocks or long blocks for peace of mind.

Engine Bare Blocks: A Third Option

An engine bare block is exactly what it sounds like: just the block casting. You may be able to opt for an engine bare block if you’re rebuilding a custom engine or if you’re reusing all internals. Bare blocks require the most labor and expertise. 

Common Mistakes Buyers Make

• Choosing short blocks to save money, but spending more later on additional repairs, labor and downtime
• Reusing worn cylinder heads
• Ignoring labor costs + transportation costs 
• Buying mismatched engine codes

Frequently Asked Questions (FAQs)

What is the main difference between long block and short block engines?

The main difference is component coverage. A long block includes the cylinder head and valve train, while a short block includes only the bottom end.

Is a long block better than a short block?

In most cases, yes. A long block reduces risk, labor, and downtime, especially for commercial equipment.

Can I install a short block myself?

Only if you have advanced mechanical skills and access to proper tools and machining services.

Is a remanufactured short block reliable?

It can be, but quality varies. Always verify rebuild standards and warranties.

When should I choose an engine bare block?

Only for custom or specialized rebuilds where all other components are known to be reusable.

We offer a wide selection of short blocks, long blocks, and engine bare blocks for top heavy equipment brands. Browse our full parts catalog or email us at contact@expertdieselparts.com for help and availability.

The information provided in this article is for general guidance only. Always refer to your machine’s manual or consult a qualified mechanic before performing any maintenance or repairs. We are not affiliated with or authorized by Bobcat Company. All trademarks are used descriptively to indicate part compatibility.