JDM engines stand for japanese domestic motors. Many import tuners have already changed to these engines. Many more sport compact enthuaists will look hard at purchasing these engines. Some people buy a jdm engine at rebuild time or simply to increase 10 or more horsepower, depending on the vehicle. JDM engines are generally tuned for a little more power than american engines. This is due to the company choosing to do so or emissions restrictions being tighter here. Most european cars are under the same stipulation. The jdm engines bought are usually used engines shipped over from main land japan with low miles. Beware as the condition of some of these engines may not be good. Purchase from someone reputable that stands behind the engine. Nothing is worse than spending the money to find out you have a bad engine in a month after installing.
These engines prices vary from each place that you check. Swapping to jdm engines is usually not that hard but a good skilled mechanic is always useful. Some people with a little less money just invest in aftermarket parts for the american engines. This will usually be a better bang for your buck. Figure out the power gain per dollar in each instance. Most people will look at using a jdm engine if they have problems with their current engine. In the right situation this makes a lot of sense to switch to the jdm engine as an american engine replacement may cost a similar amount of money. JDM engines are becoming a very popular alternative to standard domestic engines.