Replacing an engine in a car or truck can be a difficult process, especially for someone with little or no knowledge of the inner workings of an automobile. A person with no experience should consider doing the job under the direct guidance of an experienced mechanic or a person who has performed this procedure before. If this is not possible, he or she should do as much research as possible about the replacement process before undertaking this task. Obtain a maintenance manual for the vehicle being worked on, and become familiar with all the parts, procedures, and tools necessary for replacing an engine.
Before beginning the process of replacing an engine, decide what type of engine you will replace the old one with. A car owner can buy a new engine or a used one, and each choice has advantages and disadvantages. Buying a new engine is likely to help the car owner avoid more engine problems, but this option will be significantly more expensive. Buying a used engine for installation will cost far less, but it is difficult to gauge the quality of a used engine; it may end up causing just as many problems down the road. A third option that avoids replacing an engine is rebuilding the current engine, but the success of such a process will depend on how much damage is present in the engine.
The tools necessary for replacing an engine are fairly minimal, but some specialty tools may be necessary if the used engine has some wear. If the engine parts need machining, it may be wise to send the parts out to a machine shop rather than attempting to do it onsite without the proper tools. Remember too that if one part of the engine is damaged, chances are another part of the engine is damaged as well. This is particularly true of head gaskets, so a thorough inspection of the engine will be necessary.
Engine mounts should be carefully inspected and replaced if necessary before installation. Even if the bolts look undamaged, it may be wise to replace them anyway, as wear can be difficult to determine just by looking. All fluids in the engine should be flushed and replaced as well, and fresh oil will need to be in the engine and primed properly before starting it for the first time. Get a wiring guide to make sure all electronics are hooked up correctly, and do not hook up any electronics to the battery until all work is finished.