This question comes up all the time so I want to create a search-friendly FAQ to answer it.
Q: Can I swap the engine in my car or motorcycle and get away with it?
A: It depends.
Cars and motorcycles have different rules and procedures sometimes regarding their documentation and imported vs. domestically produced vehicles are also documented differently.
All motor vehicles are issued with a registration document upon successful vehicle registration and that contains certain information about the engine which will be seen when the vehicle is presented for inspection. Also, a rubbing is taken of certain numbers when the vehicle is first registered and this rubbing remains on file at the government inspection station responsible for processing that first registration.
Let’s deal with cars first.
1. Imported
Recorded information:
Manfacturer month and year
Engine capacity, ie. swept volume.
Fuel type
Transmission type (auto or manual)
VIN (vehicle identification number)
After 2007, engine number
Registration after 2007 is supposed to include the engine number if the manufacturer provided that information on their shipping documents. It’s not known if a rubbing will be taken of the stamping if the number is recorded at the time of customs inspection. Inspection station has no record of the engine type beyond the cylinder capacity noted on the import documents and they would have to go to the importer for any such data.
Subsequent inspection:
When the vehicle is more than five years old it is subject to inspection on an annual basis. After ten years it’s six monthly. Vehicles that run on LPG must be inspected annually, regardless of age. If you are within the date specified on the notice to inspect, you may choose to go either to the DMV for inspection, or any certified outside testing station. These stations are run privately. You can apply at a private station for an appointment beyond the specified date, but then you must either inspect at that particular station, or at the DMV center where the vehicle was originally registered.
If the car is stolen and recovered it must be inspected at DMV in order to clear it from the stolen list, whether or not the registration was canceled.
What the law says:
You may not replace the engine with another of a type different from that in the original specification. Therefore it’s illegal to switch to any other engine type except the exact same one the vehicle was imported with. There is a process by which you can apply to have the engine number changed if there is one recorded on the registration.
The reality:
The DMV has no idea what engine was actually fitted to the vehicle beyond it’s cylinder capacity. They probably don’t know where to look for that either. Of course if you fit an engine that screams “Quad Overhead Cam, 5.6 Liter!” from it’s cam cover and the registration says 1.6 liter, you may get noticed.
An independent station has even less idea than the DMV, but again they may or not notice a radically different configuration than the original. I have seen vehicles pass with a completely different engine, different transmission type, different body color and all of the above. YMMV.
If there is no engine number on the registration there is no process by which you can inform the DMV you have swapped a legal engine into the vehicle.
Vehicles imported after 2007 may or may not have an engine number recorded on the registration. It depends on how easy it was to find the number and whether or not someone felt like doing it that day. If you need to replace an engine in a vehicle with the engine number on the registration you are going to need to enlist an agent to negotiate the maze of paperwork to prove the engine was legally imported and is the exact same type as the original.
2. Domestic production or assembly
Recorded information:
Manufacture month and year
Engine capacity, ie. swept volume.
Fuel type
Transmission type (auto or manual)
Engine number
VIN
Inspection includes the engine number, and a rubbing is taken of the stamping and kept on file. Inspection station has no record of the engine type beyond the cylinder capacity noted on the import documents, but they do have access to this information via the manufacturer.
Subsequent inspection:
When the vehicle is more than five years old it is subject to inspection on an annual basis. After ten years it’s six monthly. Vehicles that run on LPG must be inspected annually, regardless of age. If you are within the date specified on the notice to inspect, you may choose to go either to the DMV for inspection, or any certified outside testing station. These stations are run privately. You can apply at a private station for an appointment beyond the specified date, but then you must either inspect at that particular station, or at the DMV center where the vehicle was originally registered.
If the car is stolen and recovered it must be inspected at DMV in order to clear it from the stolen list, whether or not the registration was canceled.
What the law says:
You may not replace the engine with another of a type different from that in the original specification. Therefore it’s illegal to switch to any other engine type except the exact same one the vehicle was equipped with when it was registered. You must apply to the DMV for an update to the registration with the new engine number. At this time you have to produce documentation on that engine type and prove it is identical to the original.
The reality:
The DMV has no idea what engine was actually fitted to the vehicle beyond it’s engine number and cylinder capacity, but they do have access to that information from the manufacturer. If you present for inspection and everything looks stock under the hood, and the car is not riced out, chances are they will not check the engine number. DMV does have a rubbing of the original engine number stamping and can therefore investigate any suspicion they might have that the engine number is a fake. You cannot pass inspection if it turns out to be faked, removed or falsified in any way. Heavy fines and vehicle confiscation are also possible.
An independent station has even less idea than the DMV, but again they may or may not notice a radically different configuration than the original. I have seen vehicles pass with a completely different engine, different transmission type, different body color and all of the above. YMMV.
In the event that you do fit an identical replacement engine, you will need the services of an agent to help with the long and complex paperwork proving your new engine is identical to the old one. While you may be able to pass inspections with an undocumented engine in your car, a smart buyer should be looking for it.
Notes:
Taiwan and Japan cooperate in the area of vehicle theft. Since a great many vehicles stolen in Japan used to end up in Taiwan, or at least parts of them, the police here can and will check back with Japan if they find a VIN or engine number to be suspicious. If you buy an imported engine from a dealer or junkyard you should check the import paperwork is genuine.
Anyone can import any engine from overseas through legal channels. Import tax is not even very high. Getting that engine number onto your registration document is complicated at best.