Mike Flanagan walked a tightrope of stranded base runners for 6 1/3 shutout innings in his strongest outing of the season and Rick Dempsey hit a home run in the second inning as the Baltimore Orioles beat the Minnesota Twins, 1-0, before 30,556 in Memorial Stadium tonight.

Don Aase was nearly perfect, as usual, preserving the shutout with 2 2/3 innings of one-hit relief that earned him his major league-leading 25th save. With one more save, Aase will tie the Orioles club record set by Tim Stoddard in 1980.

But the story of this game was Flanagan, who allowed at least one batter to reach base in each inning he pitched, but weathered each threat by stranding eight runners in six innings. The left-hander, who won only one of his first 13 starts, is 4-6.

The victory moved the Orioles to 48-42 and back into fourth place in the Al East ahead of Toronto, a 9-3 loser to California. Baltimore is still nine games behind division-leading Boston, but the mood in the clubhouse was optimistic.

"New York is closing on Boston, and maybe that will put some pressure on the Sox," said Dempsey, whose homer produced his first RBI in 15 games. "We have got to hang on, and hopefully sneak in come September."

Dempsey hit a breaking ball by Neal Heaton into the left field seats with one out in the second inning for the game's only run. The Orioles never advanced a runner past first from that point, but Flanagan and Aase held on for the Orioles' fourth shutout of the season.

" Flanagan had that good sinking fastball," said Orioles Manager Earl Weaver. "And he got the big out when we needed it tonight."

Twins pinch hitter Mark Salas came within 10 feet of tying the game in the ninth against Aase, but Lee Lacy hauled in his fly ball in deep right.

"I knew I hit it good," Salas said. "I'll have to go into the weight room and pump some more iron."

After Aase allowed a pinch-hit single by Randy Bush, he forced Greg Gagne to fly out to left to preserve the victory, the seventh for Baltimore in its last 11 games.

For Heaton, the game was a disappointing sort of de'ja vu. The last time he had faced the Orioles -- July 6 -- he lost a 1-0 decision to Ken Dixon and Aase. This time he allowed only five hits but got little support and his record dropped to 3-9. The Twins are 38-53.

"I pitched well, but we just hit the ball right at people," Heaton said. "I did my job. It's not my problem."

The Orioles failed to score in the first inning for the 25th consecutive game but took the lead in the second on Dempsey's ninth homer of the year and first in 18 games.

"It was a breaking ball down," Dempsey said. "I was fortunate that I got down on it and hit it well."

The Twins got a runner to third in the fifth and sixth innings against Flanagan, who tied his season high of six strikeouts. In the fifth, third baseman Floyd Rayford pulled first baseman Juan Beniquez off the bag on Kirby Puckett's routine grounder with two outs. Gary Gaetti's single to left put runners on the corners, but after Kent Hrbek lofted a foul ball deep into the right field stands, Flanagan got him to ground out to second.

The Twins threatened again in the sixth against Flanagan, who had thrown 94 pitches through five innings -- he finished at 117 -- and was visibly tiring.

Tom Brunansky singled to open the inning, was sacrificed to second by Roy Smalley and went to third on Mickey Hatcher's grounder to second baseman Alan Wiggins. But Steve Lombardozzi grounded out to second as Flanagan got away again.

Weaver had tired of Flanagan's escape act by the seventh, when Lacy was chased to the wall by Tim Laudner's fly ball and the left-hander walked Gagne. Aase came in and walked Puckett, the first batter he faced, but then got Gaetti to ground into an inning-ending double play. In the eighth, he set the Twins down 1-2-3, the only time Minnesota were retired in order the entire game.

Twins left-handed reliever Juan Agosto, who was called up from Class AAA Toledo earlier in the week, was sent home today after being diagnosed as having chicken pox.

A club spokesman said a decision on Agosto's roster status would not be made for a few days.