CINCINNATI -- The San Francisco Giants are headed home following the six-game road trip with a suddenly resurgent offense and plenty of momentum in tow.

"We've got three or four guys hot at one time," said Giants manager Bruce Bochy. "This is a little more like who we are. It made for a nice road trip."

Right fielder Hunter Pence and first baseman Brandon Belt homered as the hot-hitting Giants defeated the Cincinnati Reds 9-8 in the finale of a four-game series on Sunday afternoon at Great American Ball Park.

San Francisco (20-18) won the final three games in the series, scoring 10, 11 and nine runs in the process.

"The boys swung it well here," Bochy said. "It's hard to put up these types of runs."

Right fielder Jay Bruce and second baseman Brandon Phillips homered for Cincinnati, which has lost three straight for the fifth time this season.

Right-hander Yusmeiro Petit (1-0) pitched three innings and was awarded the victory.

"He did what long guys do, he calmed things down," Bochy said.

Right-hander Santiago Casilla struck out three batters in the ninth inning on nine pitches for his ninth save.

The Giants, who scored 21 runs in the previous two games, erupted for four runs in the second inning on Sunday.

Shortstop Brandon Crawford's RBI single and a run-scoring double by center fielder Gregor Blanco put San Francisco ahead 2-0.

The Giants' barrage paused for a 24-minute rain delay, then resumed when left fielder Nori Aoki delivered a two-run single to make the score 4-0.

San Francisco sent nine batters to the plate in the second, pushing Reds starter Anthony DeSclafani's pitch-count to 51 through two.

The Giants added two runs in the third on Pence's two-run homer. That gave the Giants a 6-1 lead after the Reds pushed across a run in the bottom of the second.

DeSclafani (2-4) left after three innings, having allowed six earned runs.

The Giants outscored Cincinnati 17-6 in the first three innings during the four-game series.

"There are a lot of balls in the air right now with the pitching staff," said Reds manager Bryan Price. "If we're going to be competitive we have to get a lot out of our pitching staff. Who that 12 are going to be is up in the air."

San Francisco starter Chris Heston allowed five earned runs and seven hits in two-plus innings.

The Reds fought back with four runs in the bottom of the third. Left fielder Marlon Byrd and Bruce contributed RBI singles in the inning.

It was clear early in Sunday's game that both bullpens were in for a long day.

Phillips cut Cincinnati's deficit to 7-6 with his second homer in the fifth off Petit.

Later in the inning, pinch hitter Skip Schumaker's double to right-center nearly tied the score, but the ball bounced into the stands for a ground-rule double, forcing the runner back to third.

Aoki's bunt single on a safety squeeze play scored Crawford from third to increase the Giants' lead to 8-6 in the seventh.

"That was his call," said Bochy. "He saw they were playing back. The key for us today was we kept adding on. They punched back, we punched back."

After narrowly missing a grand slam in the third, Bruce connected for this seventh home run off Jeremy Affeldt in the seventh, making the score 8-7.

Bruce went 3-for-4 with a homer and two RBIs on Sunday.

"Off the bat I thought the ball (in the third inning) was gone, but the cross wind knocked it down," Bruce said. "That's baseball. It is a game of inches. Every little thing counts whether you think it does or not."

Belt's third home run in the series, a solo shot off Tony Cingrani in the eighth, got that run back. He went 3-for-4 with a double, homer and RBI on Sunday.

"I'm getting back to doing what I do best, seeing the ball well and putting good swings on," Belt said.

Including his third-inning homer on Sunday, Pence went 4-for-8 with a homer, double, two RBIs and scored five runs since coming off the disabled list on Saturday.

"Having Hunter back has been a big shot in the arm," Belt said.

NOTES: Reds RF Jay Bruce had his first three-hit game since Sept. 25, 2014. ... Reds CF Billy Hamilton, batting .212 with a .264 on-base percentage before Sunday, was dropped from the leadoff spot and batted eighth. He went 1-for-3 Sunday to improve his average to .214. SS Zack Cozart batted leadoff for the second straight day. ... Giants CF Angel Pagan, who left Saturday's game in the sixth inning with back spasms, was given a day off on Sunday but was fine to play, according to manager Bruce Bochy. ... San Francisco scored 10 or more runs in two straight games for the first time since Aug. 3-4, 2012, at Colorado. ... Cincinnati is 21-11 vs. the Giants over the past five seasons. ... Including Sunday's delay, there have been six rain delays this season at Great American Ball Park, totaling 10 hours and 40 minutes.