Possible if its on a Formula car chassis, not on a Civic, because the drag at 300km would require lots of power to overcome, considering the Civic is not aerodynamic to begin with.
Air resistance increases as the speed increases, which is why if you look at top speed runs by Veyrons and the likes, the speed climbs VERY slow beyond 300km/h. In fact is rather slow above 280km/h
Point of reference: McLaren F1
Coefficient of drag: 0.32
Weight: 1100kg give or take with driver
Power: 627bhp give or take
TOP SPEED: 315km/h
Civic 2008
Coefficient of drag: 0.36
Weight: 1179kg give or take
Power:
If you look at the McLaren, you know you need more than 627bhp to hit 300km on the Civic. Why? Higher drag, higher weight.
One of the most powerful K series engine I've seen, fully naturally aspired, is 301bhp and it is a 10 second car.
Humble Performance Project Blue Balls K24/K20 300+ Pump Gas !!!!! - Honda-Tech
Your friend can hit 300km/h in his super modified Civic? My shit can fly.