Pedro Alvarez also went deep for Pittsburgh, which split the four-game set in Philadelphia by winning the last two. The surprising Pirates, seeking their first winning season since 1992, are 40-35 and second in the NL central.
Burnett (9-2) allowed three runs and six hits, striking out seven. It's the first time a Pirates pitcher has won eight in a row since Dock Ellis in 1974.
Joel Hanrahan tossed a scoreless ninth for his 20th save.
Eric Kratz and Pence hit homers for the Phillies.
The Pirates jumped on Kyle Kendrick (2-8) for five runs before he recorded a second out in the first.
