HOUSTON (AP) -- Lance Berkman hit a grand slam in an eight-run seventh inning after San Francisco ace Tim Lincecum left the game with an injured knee and the Houston Astros won their sixth straight game, beating the Giants 12-4 on Tuesday night.

Associated Press

Lance Berkman's grand slam was part of an eight run rally in the seventh inning.

The Astros hammered four San Francisco relievers to blow open what had been a tight pitching duel between Lincecum and Astros ace Roy Oswalt (10-8).

The Giants led 3-2 with one out in the seventh when Alex Hinshaw walked Ausmus to spark the rally. Giants manager Bruce Bochy brought in Tyler Walker (4-7) to relieve, but pinch-hitter Hunter Pence singled and Mark Loretta walked to load the bases.

Left-hander Jack Taschner replaced Walker and Darin Erstad blooped a two-run single to left and Pence scored right on Ausmus' heels. It was a less violent version of the end of the Astros' 5-4 win over the New York Mets on Aug. 2, when Pence followed Loretta across the plate in a three-way collision with Mets catcher Ramon Castro.

Miguel Tejada singled to load the bases again for Berkman, whom Lincecum had struck out twice.

This time, Berkman drove a 3-1 pitch off the brick facade in left field, his 24th homer this season and his fourth career regular-season grand slam. Berkman has homered in two of his last three games after going 33 games without one.

Geoff Blum doubled, Geno Espelli relieved Taschner and Ty Wigginton added a two-run homer to right. Wigginton had three RBIs in Monday's 3-1 win, including a solo homer.

Pence added a solo homer and Tejada had an RBI double off Espelli in the eighth.

Randy Winn drove in two runs and Aaron Rowand hit a solo homer in the ninth for the Giants.

Erstad had an RBI double in the third and scored on an error by second baseman Emmanuel Burriss to give Houston a 2-1 lead.

Lincecum, a .163 hitter, singled up the middle in the fourth and scored on Winn's double to right center. Lincecum struck out the side in the fourth and had all the Astros baffled.

Fred Lewis and Molina started the fifth with singles. One out later, Oswalt walked John Bowker to load the bases and Lewis scored on Rich Aurilia's fly to right to put the Giants up 3-2.

Ausmus led off the Houston fifth and drove a 3-1 pitch back to the mound. Lincecum tried to dodge it, but the ball nailed him on the side of his knee. Ausmus was out on the play, but Lincecum hit the ground and later limped to the dugout. He was replaced by Keiichi Yabu, who got the last two outs.

Yabu and Hinshaw held Houston scoreless in the sixth, but the Astros put together their highest-scoring inning of the season in the seventh.

The Astros have won 10 of their last 12 games and have their first six-game winning streak since April 20-25. They improved to 60-59, their first time over .500 since June 10.

Notes:@ Astros 2B Kazuo Matsui left after two innings with a sore back and was replaced by Loretta. ... The Giants have committed 30 errors in their last 36 games. ... Ausmus became the 25th catcher to score 700 runs.