The mechanic and the cardiologist

A mechanic was removing a cylinder-head from the motor of a Harley motorcycle when he spotted a well-known cardiologist in his shop. The cardiologist was there waiting for the service manager to come and take a look at his bike when the mechanic shouted across the Garage, 'Hey Doc, want to take a look at this?' The cardiologist, a bit surprised, walked over to where the mechanic was working on the motorcycle. The mechanic straightened up, wiped his hands on a rag and asked, 'So Doc , look at this engine. I open its heart, took the valves out, repaired any damage, and then put them back in, and when I finish, it works just like new. So how come I make $39,675 a year and you get the really big bucks ($1,700,000) when you and I are doing basically the same work?' The cardiologist paused, smiled and leaned over, then whispered to the mechanic...

 'Try doing it with the engine running.