What's the difference? a valve is a valve!
(It's a wee bit different in the medical profession.)
Morris was removing some engine valves from a car on the lift when he spotted the famous heart surgeon Dr. Michael DeBakey, who was standing off to the side, waiting for the service manager.
Morris, who was somewhat of a loud mouth, shouted across the garage, "Hey DeBakey...Is dat you ? Come over here a minute."
The famous surgeon, a bit surprised, walked over to where Morris was working on a car.
Morris in a loud voice that all could hear, said argumentatively, "So Mr. fancy doctor, look at this work. I also take valves out, grind 'em, put in new parts, and when I finish this baby will purr like a kitten. So how come you get the big bucks, when you and me are doing basically the same work?"
DeBakey, very embarrassed, walked away, and said softly, to Morris,...
"Try doing your work with the engine running."
:: Author unknown