I have only ever come across this 5-game series (1984 ECR1, NJN vs PHI, NJN win 3-2), where the road team won every game.
Has this ever happened in a 7-game series?
(In recent memory, one series in which the first 4 games were won by the road team was HOU vs DAL, 2005, WCR1. But the next 3 games were won by the home team.)