Primeira Liga: Vitoria Guimaraes 1 Braga 0
The fixture is one of the most eagerly anticipated in Portugal and fifth-placed Guimaraes claimed bragging rights in front of 14,000 spectators at Estadio Dom Afonso Henriques.
After a scoreless opening half, Valente, who returned to the starting line-up following his one-match suspension, rose highest from a corner to head Guimaraes into a 66th-minute lead - an advantage the hosts never relinquished.
The victory saw Guimaraes move four points clear of sixth-placed Belenenses, who face league leaders Benfica on Saturday.
Braga remain fourth with 53 points following a first loss in four games.