my engine is a 118 HP HTTC CNC ported and i installed valves Doherty Machine into the air vents of the heads engine. the problem is that, when i open wide full throttle in fifth gear, at about 230 km / h, there is an oil leak from vents. Why? I tried to enlarge the bolt holes screwed in the heads of the engine but can not figure out what the problem is. can you help me?