"This is a big win for us and I'm excited," Carpenter said. "My breaking ball moved well. My cutter was good. I was on the corners and making quality pitches all night long. When you do that you are going to have success."
The win gives the Cardinals a chance to clinch their first World Series crown since 1982 by winning games four and five at home on Wednesday and Thursday.
"Number one, you credit Chris Carpenter and number two, some of our guys aren't hitting too well right now," Tigers manager Jim Leyland said.
"If we don't swing the bats better they will go up 3-1. I think we will swing the bats better. We're not conceding anything."
Jim Edmonds also chose his moment to find some form.
After hitting only .156 against left-handers this year, he hit Tiger southpaw starter Nate Robertson for a two-run double down the right-field line in the fourth inning for all the scoring Carpenter would need.
"The biggest contribution we had was Jim's base hit," Cardinals manager Tony La Russa said.
"The bigger the moment, the more likely it is he is going to produce. In moments like this he doesn't get awed. He just gets the job done."
A throwing error by Detroit relief pitcher Joel Zumaya allowed two runs to score in the seventh, and Tiger reliever Zach Miner's wild pitch allowed Japan's So Taguchi to cross home plate in the eighth inning to complete the rout.
Carpenter chips in
Carpenter, 15-8 this season with a 3.09 earned-run average, improved to 3-1 in the playoffs and brought an emotional lift to his teammates.
"My job is to go out and pitch and compete. We came up with a good game plan. The key is to execute that plan," Carpenter said. "If you execute pitches you're going to have success. If you do that, it's tough to hit."
Carpenter, who missed the Cardinals' 2004 World Series loss due to injury, won the National League Cy Young Award as best pitcher in 2005, and the ace has made a case for a repeat honor.
"He had good command. He has got a lot of weapons and everything moves," La Russa said. "He's so strong between the ears. Nothing fazes him. Besides his physical talent he has great game, great heart, great guts."
The Cardinals would have the worst record of any World Series champion after a late-season fade to 83-78 that nearly cost them a playoff spot.
The Tigers seek their first World Series title since 1984 after 12 losing seasons in a row, including an American League-record 119 losses in 2003.