A hungover flock of Baltimore Orioles -- now into the meaningless wrap-ups games of the regular season -- managed to split today's doubleheader with the Cleveland Indians.

Dennis Martinez, who was dealt his normal poor hand of no offensive support, dropped his 16th game as the Birds opened with a 4-3 loss. Mike Flanagan two-hit the visitors for eight innings in the finale to win his major league-leading 23rd game, 3-1.

"I don't know how I did it," was Flanagan's reaction to the victory. "After last night (the Orioles' American League East pennant celebration), I was dragging a bit."

The Indians would be hard-pressed to support that premise.Both hits off the southpaw were marginal. Left fielder Gary Roenicke failed to hustle and watched a fly ball take a short hop in the fifth; in the seventh, Roenicke barely missed a fine diving attempt at catching Ron Pruitt's fly.

Flanagan will get one more start as he attempts to tie the club record of 24 victories held by Mike Cuellar and Dave McNally.

Flanagan received offensive aid in the form of RBI from Al Bumbry, Lee May and Rick Dempsey en route to notching Baltimore's 100th victory. Oriole Manager Earl Weaver celebrated his second milestone of 1979. On opening day, he managed his 1,000th victory.

Baltimore has now won at least 100 games four times under Weaver's 11-plus-season reign. Flanagan's four-strikeout, four-walk effort was marred only by Cleveland's run in the seventh. After Pruitt reached on the double off Roenicke's near-miss, he gained the final 180 feet courtesy of two infield outs.

Otherwise, Flanagan baffled the visitors with his usual assortment of change-ups and breaking pitches. He got the lead-off man out seven times and only twice watched an Indian progress as far as second base.

"It all goes back to my changeup," Flanagan said. "If I get those over the hitters don't seem to be as agressive to the fast ball. They don't want to be fooled by the off-speed stuff, so they hold back a little. That way, I got a lot of flies to the outfield."

Flanagan was bothered by blisters on both of his feel and the middle finger of his throwing hand. Those ailments prompted him to voluntarily yield to reliever Don Stanhouse in the ninth.

"I never worry when Stan the Man Unusual comes into the game," Flanagan said. "He's been reliable for quite some time."

Stanhouse, who also pitched the final inning of the opener, served a one-out walk to assure his 21st save. He wrapped things up by striking out Gary Alexander and getting Wayne Cage on a ground ball.

Bumbry's second-inning two-out single scored Lee May, who led off with a base hit. In the third, Ken Singleton doubled to lead off, reached third on Eddie Murray's single and scored on May's sacrifice fly.

The Birds added an insurance run in the sixth. May opened with his second single. A walk issued to Billy Smith by Dan Spillner advanced May to second. Then Wayne Krenchicki planted a fine sacrifice bunt to put both men in scoring position.

Rick Dempsey followed with one of his two broken-bat singles. "The bats weren't cheap, the pitches were hard," he said. May scored his second run for a 3-0 count.

The Orioles were a different bunch in the opener. Martinez, who earned the dubious distinction of being Baltimore's only pitcher with a losing record this season, got himself out of several early jams as he nursed a 3-1 lead until the seventh.

Baltimore had a near-triple play in the fourth, settling instead for two outs. Jim Norris, who beat the throw to first, to stifle the hat trick, stole second. Tom Veryzer's single scored him.

The Indians knotted the score on designated hitter Cliff Johnson's two-run homer in the seventh. Doubles by Cage and Dave Rosello in the eighth provided the winning run.

The Orioles reflected the Saturday night festivities in the late innings. Dave Skaggs' double represented the only Oriole hit in Baltimore's final 18 plate appearances.

In the seventh, Singleton grounded out with the bases loaded -- thanks to two walks and Skaggs' hit -- to shut down the only serious Oriole scoring threat.