If you are in the market for a car engine there a several major things you should look out for. Most of the engines available from the local auto parts stores can be specifically ordered for your make and model of car. These are available in long blocks and short blocks. The long block will come complete with everything except the tin and sheet metal parts such as valve covers, timing gear cover and oil pan. Once the covers are in place the engine will be ready to drop in.
The short block will not have heads or any of the tin or sheet metal covers. If the heads on your current engine are in good shape it may be cost effective to buy the short block and have the old heads rebuilt and reuse them on the replacement engine. Some of the major auto parts stores will be able to do this in house or at least be able to send them off for you.
When buying one of these engines keep in mind that most of them are re-man engines. These have been re-manufactured. There are a lot of companies that offer re-man engines so make sure the engine you are ordering is from a well-known respected company. Make sure they offer a warranty on the re-man engine and any parts that may come with it such as a new oil pump. Most of these engines typically have at least an 18,000 mile warranty with the option to extend the warranty for a higher price. Some auto manufacturers offer re-man engines and this may be the best way to go because they only re-man engines for the cars they build unlike some of the other companies that re-man engines for all makes and models. You can be sure the re-man that came from the auto manufacturer was fitted with the original equipment and no aftermarket parts.
If you are thinking of buying a car engine from a private seller make sure the engine is in good operating shape. Look for problems like stains on the block that may have been caused by excess heat or oil leaks. Make sure the engine was not in a car that was in a rollover accident. If the car was in a rollover accident the engine could have run for a short time upside down which would have allowed the crank shaft to run without oil causing damage to the bearings and shortening the life of the engine. Also look for any aftermarket performance accessories that have been added to the engine, because if you find them the engine was probably ran hard regularly. Was the engine stored outside? If it was it may have moister in the cylinders or crank case that can cause rust. If there is any rust in the engine it will need to be completely rebuilt costing more than it is worth. Another thing to check are the spark plugs. Pull out the plugs and check if any of them are looking burnt or have large amounts of carbon building up on them which means the engine was not running right before it was removed from the last car it was in. Make sure the engine was out of the exact model of car with the same transmission to be sure you will not need to buy extra parts to make the engine fit properly. It will be a good idea to ask the engines owner if you can have a professional inspect the engine and give his point of view on the engine. A seasoned mechanic may easily see something that you can’t and will save a lot of time and effort.