be all brawn and no brain(s)

To have great power or physical strength but lack mental acuity or intelligence. He may have been a good football player in high school, but he was all brawn and no brains, so he didn't get into any colleges. Why did you ask Todd to come up with a solution to this complex problem? You know that guy is all brawn and no brain. Eh, he's just all brawn and no brain, your typical jock. But if you want to go out with someone who can discuss modernist literature, I'm your man!