Perhaps no victory in baseball is sweeter than slaying the New York Yankees in their own Bronx palace. The Yankees mean excellence, but they also stand for haughtiness and victory through cash transaction.

Ever since the Bombers returned to power eight years ago, it's been the wish of every American League contender to throttle the pin stripers in their ritzy blue abode. Here, amidst statues to Hall of Famers and scoreboard testimonials to Ruth, Gehrig, DiMaggio, Mantle, Maris, Munson and Jackson, many a team has come to grief.

Just one day ago, the Baltimore Orioles were a tight team. After losing here Friday, they had to have nightmares about seeing their five-game AL East lead chopped to three games, or even one, by the hungry Yankees.

Now, in less than 24 hours, the Orioles have not only slain the Yankees, beating them three times in less than a day, but they have come mighty close to putting the AL East pennant race to sleep.

After a 5-3 victory today, built on a freakish five-run second inning against Dave Righetti, the Orioles lead New York by seven games (and eight in the lost column). All-but-extinct Milwaukee is 7 1/2 games behind, nine in the lost column. Only the Tigers, 5 1/2 games behind (but seven in the lost column) are still breathing perceptibly. Should the Orioles finish 11-11, the Tigers, Yankees and Brewers would have to go 16-3, 18-2 and 18-1, respectively, to beat them outright. That's a big lead for a team that's won 16 of 19 and 23 of 29.

This victory, following an 8-4, 3-1 twinight sweep Saturday, was all the sweeter for the Orioles because the Yankees were equal partners in their own defeat. Twice, Yankee runners were out at home testing the arm of center fielder John Shelby; a third was out at second after Shelby's throw to home was cut off.

After an inning, few of the 45,649 fans here would have bet the Orioles' Mike Flanagan would beat Righetti.

Flanagan escaped the first because Shelby nailed Willie Randolph at home on Ken Griffey's single. Righetti struck out two in his first inning and "looked like he was going to have a 14-strikeout game," according to the Orioles' Jim Palmer.

Instead, Righetti never survived the second inning.

Eddie Murray opened with a checked-swing hit into center past Righetti's glove. Ken Singleton's single put Orioles at the corners with one out.

Righetti then walked .230 hitter Rich Dauer to load the bases. After getting ahead of Todd Cruz, 0-2, Righetti threw a disastrous changeup that Cruz poked over third for a two-run double. Dave Winfield lackadaisically threw to the wrong base, giving Cruz second--a mistake that helped open up the inning.

"Why get beaten on your third-best pitch?" wondered Palmer.

The Orioles thought Yankees Manager Billy Martin called the pitch. "He called every pitch until they were down, 4-0, then he stopped," snickered Singleton. Amusingly, Martin blamed catcher Rick Cerone and "the bad call" for helping lose the game.

Martin certainly masterminded the next foulup. Down only 2-0, he pulled in the infield. Perhaps he wanted to prove he hadn't been wrong in using the same strategy in the sixth inning of a tie game the night before. Then, a bloop hit landed just over the infield for the game-winning hit. This time, Martin's strategy failed by inches again.

Rick Dempsey hit a routine chop that ticked off the glove of third baseman Bert Campaneris, who mistimed his leap, for a two-run single.

Speaking of Martin's two precipitous infield-in decisions, Palmer said, "It was dumb. Both times. Billy panicked."

Martin has always injected himself into the game on any pretext. To second-guess him is to question his basic style.

Still, it was a bizarre team he fielded this afternoon, a lineup that included Campaneris, 41, at third, Cerone (hitting .202), Larry Milbourne at short, Omar Moreno in center and Roger Erickson in long relief. Shades of Ruben Amaro, Jake Gibbs, Jerry Kenney, Roger Repoz and Dooley Womack.

"Can you immagine Detroit or Milwaukee putting a lineup like that out there in a game that might be their last stand?" asked Palmer.

Shelby singled and Ripken knocked out Righetti with an RBI single to right. That five-run lead was just what the sore-kneed Flanagan needed. Flanagan (11-3) lasted 8 1/3 innings and struck out eight, despite allowing 11 hits.

"My knee is sore," said Flanagan, who threw 107 pitches. "I'll see a doctor in Boston tomorrow." He also has an arthritic hip.

The Orioles outdid themselves in Flanagan's defense. Dauer made both a leaping and a diving grab. Shelby's throws to home were so accurate that catcher Dempsey said it was "a tossup" whether Flanagan or Shelby had better control. "Smoked 'em both," said Dempsey, who had the ball waiting for Griffey when he tried to score on a single by Don Baylor.

Finally, in the ninth, Flanagan, pitching on three days' rest, was exhausted. He walked Winfield and gave up a two-run homer to Baylor. With a man on first and one out, Tippy Martinez entered and finished his fourth game of the series, earning his 17th save.

"My arm was numb," said Martinez. But his luck was good. Cerone hit his first pitch to the track in left for an out.

After the last Yankee ground out, postmortems were a dime a dozen.

"Scoring six off (Goose) Gossage in the ninth in the opener on Saturday was the pendulum game," said Orioles Manager Joe Altobelli.

"They just came out and played better baseball than we did," said Randolph. "They're a well-rounded club. I have . . . respect for the Orioles. In the first, I thought Righetti was going to have one of his (big) days. But Baltimore keeps its cool. They won't fold up their tent and say, 'Here he is.' Make a mistake and they capitalize."

"It's going to be very, very, very tough," said Gossage.

Maybe even tougher than that.