What to Look for When Buying a Used LS Engine


LS engines are great to purchase used, but what should you look for when purchasing one?

When buying a used LS engine, look for the quality of the oil, spark plugs, compression, and balancer. If the oil is old and dark, or the spark plugs are damaged and old, then the engine may not be in good condition. Look for rust evidence on the outside of the engine.

Quality used LS engines are relatively easy to find, if you know what to look for.

Check The Oil

When you are looking for an LS engine, check the level and quality of the oil. If the oil is low and old, then the engine may have been misused and neglected. An engine with really dark and dirty oil may have other issues that cannot be seen from the outside or checked as easily as the oil can be checked.

If the oil is dark and dirty, it may also mean that the person who is selling you the LS engine has not checked it thoroughly, and they may not know if anything is truly wrong with it. This means that they are selling you an engine that they truly know nothing about, which is bad.

Check The Spark Plugs

When looking at an LS engine, look at the spark plugs if you can. If they look really good and relatively new, then you are most likely looking at an LS engine that will work very well for a long time. If the spark plugs are dirty and broken, then you may want to pass on purchasing that LS engine.

However, spark plugs only take about an hour to change, so if the rest of the engine is in tip-top shape, then it is relatively easy to change out the spark plugs and have a well-running engine. And you don’t have to use any tools other than a 5/8 socket and a ratchet (Source).

Spark plugs are a great indicator for other issues with the engine, so don’t ignore the fact that they are dirty or broken if you find that they are. Spark plugs can indicate that the cylinder is dead, a lean condition, a rich condition, and detonation, which will cost you a lot of money to fix, and sometimes cannot even be fixed (Source).

Check The Compression

When you are looking at a used LS engine, check the compression of the engine. When you test the compression, you can confirm or eliminate the possibility of many problems the engine may or may not have.

You can check the compressor without starting it if it has been lifted off the ground high enough to manually spin it with a ratchet. However, this is slightly hard to do. But if you can turn it over with a ratchet, then you may save yourself from purchasing a low-quality used LS engine (Source).

Check The Balancer

When you are looking to purchase a used LS engine, check to see if the balancer works. If the balancer does not work, then the engine will vibrate more than it should, and the drive belts may not function as well as they should after the engine is installed.

When you check the balancer, make sure that the engine is not locked up. If the engine is locked up, then it will not work. If you can, listen to the engine run before you purchase it. This way you can determine if the engine is louder than it should be is if it actually runs, if it shakes excessively, and if it runs properly. If you are unable to listen to the engine, ask if you can turn the engine over manually.

Look For Rust

When purchasing a used LS engine, look for rust on the outside of the engine. If there is a lot of rust on the outside of the engine, or rust on the edges of the bolts, this is an indication that there is a lot of rust on the inside of the engine as well, which is not good to have when you are purchasing a used LS engine.

When you are checking for rust on the engine, also check the exhaust manifold bolts. Used LS engines often have broken header bolts, and they are not very easy to remove, which means that the engine will require a lot of work before it will work properly (Source).

Ask Questions

When you are looking for a used LS engine, ask the seller of the engine questions about it. If they do not know a lot about the engine or don’t want to seem to talk about the engine, then that is very suspicious. Ask about the mileage of the engine, what car it was removed from, and so on.

If they don’t want to talk about the engine, then it most likely means that there are many things wrong with it, and it will take a lot of money to fix, but they just want to sell it. It is in the seller’s interest to know everything about the engine they are selling because the more they know about it, the more likely they are to sell it quickly (Source).

Where to Purchase an LS Engine

Salvage yards are great places to find a used LS engine. Some salvage yards have warranties for the LS engines that you can add to your purchase, just in case the engine you get doesn’t work or fit your project needs. Typically at a salvage yard, you can talk to the seller and get information about the LS engine that you are looking to purchase, and you can negotiate a price that fits your budget.

You can also find parts for an LS engine from a junkyard. However, gathering all of the pieces required to make an LS engine typically takes a lot of time, and typically costs more than if you were to simply purchase the engine at a salvage yard. If you look for parts to an LS engine in a junkyard, you may not be able to find quality parts, which can be very frustrating. Used LS engines are great if they do not have many issues that can’t be fixed.

Will Turner

Will has an absolute passion for 4x4s and loves discovering all of the small details about each model. Will joined the Four Wheel Trends team in early 2021 and has been a valuable contributor ever since!

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