Thinking of Buying a Used Engine from Japan? Here's What You Need to Know

Posted on: 3 August 2015


Swapping stock engines for imported Japanese Domestic Market or JDM engines has always been the go-to tactic for improving the performance of countless Japanese-brand vehicles. Unlike their stateside counterparts, these engines often offer higher stock horsepower figures, more desirable internal components and a greater degree of tunability for avid gearheads.

JDM engines are commonly sourced from vehicles made and sold only in the Japanese automotive market, making them highly sought after by buyers in the U.S. If you're thinking about buying a new JDM motor for your Japanese import, there are a few things you'll need to know.

Know What You're Looking For

Before you get started, you'll need to know if the engine you plan on importing is compatible with the vehicle it's going in. Chances are you already know exactly what you want, but a little extra research doesn't hurt. Take a look at the engine options for your vehicle in its native Japanese market—some engines are a direct drop-in with little to no changes to the engine control module (ECM) or wiring harness, while others require a bit more work to achieve compatibility.

All the Pieces Matter

A reputable importer should be able to tell you what sensors, harnesses and accessories are included in the engine you're looking for. You'll want to purchase an engine that's as complete as possible; the last thing you need is an engine missing parts that are hard to get a hold of stateside.

On the flip side, you may end up with a few leftover components after getting your engine swap squared away. Depending on how many components you have left over and their value, you could offset some of the costs of your engine swap by selling these components to fellow tuners.

Checking the Goods

A reputable engine importer shouldn't hesitate to offer as much information as possible about the engine you're buying. This includes detailed photographs of the engine's exterior, its various accessories (such as the turbocharger, intercooler, air conditioning compressor, etc.) and wiring harnesses as well as a detailed description of the engine's mileage and overall condition. You'll also want to ask for pictures of the underside of the oil cap, dipstick and oil pan for a cursory glance at the engine's oil condition.

Of course, there's a good chance you won't be able to perform a detailed inspection until the engine actually arrives in the US. Once it's delivered, it's a good idea to perform the following:

  • Take another look at the underside of the engine oil cap, this time in person. Milky, light-colored residue is often the sign of a blown head gasket which is something you definitely want to avoid.
  • Check the oil itself. Be on the lookout for any signs of coolant or water mixing.
  • Inspect the spark plugs. If you don't know how to read spark plugs, now is the time to learn.
  • If the engine is equipped with a turbocharger, rotate the turbine wheels to see if there's any scraping or excessive play.

Beware of Emissions Requirements

Last but not least, you'll want to make sure that your newly-swapped engine doesn't run afoul of local and federal emissions statutes. The most important ones to consider are those from the U.S. Environmental Protection Agency. According to the Clean Air Act, engines that don't meet EPA emissions standards can't be imported unless they're modified to meet those standards or given temporary exemption for off-road use, such as racing, testing or display.

In addition, there are also regional and local emissions standards to keep in mind. For instance, the California Air Resources Board requires donor engines to be newer than the donor vehicle itself, maintain its original emissions controls (catalytic converter, exhaust manifold, etc.) and undergo a thorough smog inspection before being approved by the state's Bureau of Automotive Repair. Unfortunately, getting past these hurdles may cause a slight change in plan when it comes to your engine swap.

For more information, contact used auto parts dealers.