To get started right away determine that the registration of the new engine to traffic police is not required in that case, if the brand and model of the new engine is absolutely analogous to the previous or to that provided by the manufacturer of the car. In this situation the driver can safely change the detail without worrying about the consequences and various documents.
If you are replacing the engine is not the same, and at the instance of another model or brand of the manufacturer, you will need to contact the technical supervision of traffic police in your place of residence to obtain a special permit for the replacement parts. Law enforcement agencies will conduct a free appraisal of the vehicle to exclude the possibility of forgery or non-compliance of documents, license plates more. To register a car engine, you need to prepare a number of documents, including a statement of the owner for the work of replacement of the passport of the vehicle and certificate of registration, ID of the owner, copies of the PTS from both sides, the insurance policy for third party liability, all documents of the car owner, who confirmed that it was his property, and receipt of payment of all necessary registration actions.
If you want to replace, for example, the engine VAZ, but due to a long period of service or conditions of purchase of the car the engine number is erased, then when replacing you will not have any problems. If you put the engine identical to those provided in the configuration will not be necessary, and when scanning documents the number on the engine to verify it will not, as was done previously.
You must also remember that if you are installing the motor changes the design of the car or engine performance is significantly different from the previous one, the driver should be required to go through the whole above process, in the future to avoid issues when checking for technical inspection. This applies to all brands of vehicles and engines that are subjected to any structural changes.