Long Block vs. Short Block Engines: What’s the Difference?

It’s never a positive experience learning that your car’s engine has suffered catastrophic engine failure. Whether it was due to a blown head gasket, a manufacturer defect, or simple wear and tear, replacing an engine is a costly and time-consuming process. In fact, in most cases, car owners choose to sell the vehicle as is and move on to another. However, if you’re thinking about buying a replacement engine, you may have heard the terms “short block” and “long block” but aren’t quite sure of their meanings.

In order to clarify, let’s explore the difference between a short block and a long block. We’ll also provide a few tips on determining whether or not investing in a replacement engine is a smart financial decision.

What is a Short Block Engine?

A short block, by definition, is an engine that has been partially assembled. It starts with the engine block, which is where the combustion chambers are located. The short block will contain several individual components including a crankshaft, connecting rods, pistons, and freeze plugs. This is referred to as a full rotating assembly. Regardless of whether you have a four-cylinder, six-cylinder, or above, the short block will always contain the components that rotate inside the engine block. If the engine you are purchasing does not contain these critical components, it’s referred to as a bare block.

What is a Long Block Engine?

While the short block focuses on the engine block and bottom end rotating components, the long block goes further by adding components that mechanically complete the engine’s primary assembly. Some of the important items installed on a long block include cylinder heads, a camshaft, the valve train (which consists of all cylinder head-related hardware, the valve covers, a water pump, oil pump, and oil pan, and other components. A long block does not require the installation of fuel system components, such as an intake manifold, fuel pump, or fuel injection/carburetor. Engines that are completely assembled are typically referred to as a complete engine or crate engine in some cases.

When Should You Invest in a Short Block or Long Block Engine?

When an engine fails, it is typically due to the engine’s inability to efficiently burn fuel inside the combustion chamber. This can be caused by physical damage in the short block or the components inside. If your engine has been diagnosed as having a short block related failure, and the cylinder heads and supporting upper engine components are in satisfactory condition, then purchasing a short block is acceptable.

However, if the cylinder heads have been damaged, such as during a head gasket failure due to overheating in most cases, the long block would be best to purchase. The external parts needed in addition to a long block engine are less expensive than the extra internal parts essential to a short block engine.

When Should You Not Invest in a Short or Long Block?

Sometimes replacing an engine — either a short block or a long block — simply does not make financial sense. A general rule of thumb for any major mechanical repairs is to determine the overall value of your vehicle first. This can be accomplished by researching the ‘blue book value’ of your car online. The value will be determined based on your year, make, model, mileage on the vehicle, and the vehicle’s overall condition. Once you determine the resell value, compare it to the overall cost of repairs. If the cost of repairs is more than 50% of the overall value of your vehicle, it is best to move on to another car, truck, or SUV.

Replacing an engine is a major decision. Like surgery, it should involve a second opinion. If you’re in a situation where you’ve been told you need a new engine, contact a professional mechanic and have them complete an onsite inspection to verify. Taking this simple proactive step can save you thousands of dollars.

Next Step

Schedule Intake Manifold Gaskets Replacement

The most popular service booked by readers of this article is Intake Manifold Gaskets Replacement. YourMechanic’s technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews... LEARN MORE


The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Recent Intake Manifold Gaskets Replacement reviews

Excellent Rating


Rating Summary


35 years of experience
483 reviews
35 years of experience
Nissan Xterra V6-3.3L - Intake Manifold Gaskets Replacement - Brooksville, Florida
Professional and knowledgeable. Worked through the rain to repair shoddy work done by mechanic not associated with YourMechanic. Will always request him!
Chevrolet Cruze - Intake Manifold Gaskets - Spring Hill, Florida
Did a great job of fixing what needed to be done. Didn't tell me anything else needed to be fixed that was not necessary.


29 years of experience
105 reviews
29 years of experience
BMW X5 L6-3.0L - Intake Manifold Gaskets - Tallahassee, Florida
Aaron is very good guy that knows his job well and very understandable when asking questions that I didn't know about on this vehicle he broke it down to where things were happening to this vehicle that I wasn't sure. I would definitely recommend his service on my mechanic web site
Kia Sedona - Intake Manifold Gaskets - Tallahassee, Florida
Working with Aaron was a breeze. He was knowledgeable efficient, on time, and honest. One of the more pleasant encounters with a mechanic we've had.


20 years of experience
775 reviews
20 years of experience
Mercury Sable V6-3.0L - Intake Manifold Gaskets - Compton, California
Very professional and he knows his craft well. Would not trust anyone else but him to work on my car
Hyundai Santa Fe - Intake Manifold Gaskets - Los Angeles, California
Kenneth is great! He explains what needs to be done and takes care of my car as if it was his own. He keeps me informed while he’s working on my car and lets me know if he finds something that should be repaired. Also, like that he makes sure that I don’t get charged for unused parts or work not needed or done. Kenneth is an excellent mechanic.


32 years of experience
580 reviews
32 years of experience
Toyota Prius L4-1.8L Hybrid - Intake Manifold Gaskets - Long Beach, California
Just like the first time it was a pleasure he was pleasant he was thorough and he was reassuring I'm very happy with my mechanic and the work that he does
Ford F-150 - Intake Manifold Gaskets - Lakewood, California
Excellent service once again from Manuel Sanchez. He's very knowledgeable and efficient. It also is greatly appreciated that he is such a nice, friendly man. Thanks!

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.


Related articles

How to Prepare for the Colorado Driver’s Written Test
You You are almost ready to get behind the wheel and to learn to drive, but there’s still one thing that you need to do. You have to get your driver’s permit by taking and passing the written exam given...
What are the Car Pool Rules in South Dakota?
Car Car pool lanes have existed in the United States for a few decades, and have steadily been growing in popularity. There are currently more than 3,000 miles of car pool lanes throughout the country, spanning numerous different states. A...
P0468 OBD-II Trouble Code: EVAP Control System Malfunction
P0468 P0468 code definition The P0468 code is defined as Purge Flow Sensor Circuit High Input. Co-existing OBD-II codes may include P0440 or P0442, often indicating a loose gas cap, or P0443 through P0449, which can indicate an EVAP Purge...

Related questions

Motor mount/waterpump bolt froze
When dealing with a broken off bolt there are a few different ways to fix this. One of which involves drilling out the broken off bolt and extracting it using a reverse drill bit. Another way is to drill out...
cracked engine block
I do not think it is a cracked engine block, but a blown out freeze plug in the block or heads. Have a pressure test done on the cooling system to see where the leak is in the cooling system....
How long does it take to install a block heater?
Hi there. Installing a block heater for your vehicle depends on what type of heater you are installing. Some heaters are externally mounted to the bottom of the engine oil pan and other heaters are inside the engine oil pan....

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com