When starting the engine for the first time, have a fire extinguisher ready.
1. After installing the engine on the vehicle, carefully check the oil and coolant levels.
2. With the spark plugs removed and the ignition system disconnected (see section Checking the compression ratio) Crank the engine with the starter until the oil pressure gauge shows normal pressure or until the oil pressure warning light goes out.
3. Install the spark plugs, connect the high-tension wires and connect the ignition system (see section Checking the compression ratio).
4. Start the engine. It may take a few seconds for the fuel system to build up pressure, but the engine should start without much effort.
If backfiring occurs in the throttle body or carburetor, check the valve timing (correct installation of timing chain/belt), firing order (the order of connecting high-voltage wires to spark plugs) and the moment of ignition setting.
5. After starting, the engine should warm up to normal operating temperature. During warming up, carefully monitor for fuel, oil and coolant leaks.
6. Stop the engine and check the engine oil and coolant levels.
7. On the road with the engine running at full throttle, accelerate the car from 35 mph to 55 mph, then close the throttle fully and let the car slow to 35 mph with the throttle closed. Repeat this procedure 10 to 12 times. This will put a load on the piston rings and allow them to seat properly against the cylinder walls. Recheck the oil and coolant levels.
8. Drive carefully for the first 900 km (without high speeds for a long time) and check the oil level regularly. Usually, the engine has increased oil consumption during the break-in period.
9. After approximately 900-1100 km, change the oil and filter.
10. For the next 900 km, operate the vehicle as usual - do not take care of it, but do not overload it either.
11. After 3600 km, change the oil and filter again. Now the engine can be considered fully run-in.
(The article was copied from an online resource: BMWMAN.RU)