Yeah, definitely harder

Rico says his friend Kelley sends along this splendid one:

A mechanic was removing a cylinder-head from a Harley when he spotted a well-known cardiologist in the shop. He was there waiting for the service manager to come take a look at his bike when the mechanic shouted across the garage: "Hey, Doc, want to take a look at this?"
The cardiologist, somewhat surprised, walked to where the mechanic was working on the motorcycle. The mechanic straightened up, wiped his hands on a rag, and asked: "Doc, look at this engine. I open it up, take out the valves, repair any damage, and then put it back together. When I'm finished, it works like new. So how come I make less than forty grand a year and you get the big bucks, considering that you and I are doing basically the same work?'
The cardiologist paused, smiled, leaned over, and whispered to the mechanic: "Try doing it with the engine running..."

Rico says that, given the heart-lung machines in common use in heart surgery, the docs don't do it with the engine running, either...