... I'm getting a clunking sound when engine starts and on quick revving. Does anybody have any ideas ? It only happens on revving.

 

I'll bet you have a failed engine mount somewhere. Have someone start the car while you stare at the engine, the location of the failed mount should be obvious due to the "fall/shake" of the engine in a certain areawhen it starts. Startups should have some vibration, but severe will stand out.