Rookie utility infielder Floyd Rayford, using a borrowed bat because he couldn't find his own, hit a home run leading off the bottom of the 13th inning today to abruptly end a four-hour marathon as the Orioles beat the Oakland A's, 5-4.

Every nonpitcher on the Orioles' roster was pressed into service in this third straight one-run Baltimore victory under Cal Ripken Sr., the acting manager while Earl Weaver serves out a suspension resulting from an argument with an umpire. Rayford was one of the last to take the field, filling in on defense at third base after a spate of pinch hitting and pinch running in the ninth and 10th innings.

Ripken said he had no worries when Rayford stepped to the plate against left-handed reliever Bob Owchinko. Despite Rayford's .118 batting average, "He's a capable ballplayer," said the diplomatic Ripken.

So it seems. Swinging the bat of Lenn Sakata, who had homered earlier in the game, Rayford worked the count to 3-2, then hit the ball over the fence near the 360-foot mark. His third homer this year set a Memorial Stadium crowd of 21,780 off on a rousing round of cheers that didn't end until Rayford came out of the dugout to take a curtain call.

Even Orioles owner Edward Bennett Williams stopped in the clubhouse after the game to pat Rayford on the back.

"I had Lennie's bat 'cause I couldn't find my own," said Rayford, musing on his first major league game-winning homer. "It had some dingers (homers) in it today, I guess."

The Orioles rallied from behind twice to send this game into extra innings. Trailing, 2-0, in the sixth, they tied the game on Ken Singleton's eighth homer, a two-run drive that scored Al Bumbry, who had singled.

But the A's came back to score twice in the seventh. They got one run on Tony Armas' solo homer, which marked the fifth straight game against the Orioles in which Armas homered.

After Jeff Burroughs followed with a single, Ripken sent starter Scott McGregor to the showers and called on Sammy Stewart in relief. Stewart let in the fourth run, which was charged to McGregor, then stopped the A's the next six innings. Tippy Martinez (4-4) retired the side in order in the 13th to get the victory.

The Orioles got a run in the eighth on Sakata's third homer. That made it 4-3. They sent the game into extra innings on Bumbry's two-out single in the ninth, which scored pinch hitter Jim Dwyer from second.

The A's had opportunities to blow open the game early but twice fouled up suicide squeeze bunt attempts to squelch rallies.

In the sixth inning, Rickey Henderson was 90 feet from home after stealing second and third, his 90th and 91st stolen bases of the season. But when he came charging toward the plate with Cliff Johnson at bat, Johnson simply watched a low fast ball go by, then stepped out of the way so catcher Joe Nolan could chase Henderson back toward third and tag him out.

Johnson missed the squeeze-bunt sign. "I just assumed I was on my own," he said later. "It's a cardinal sin. Tomorrow morning I'll be sentenced to go to the guillotine at 8 o'clock and have my head chopped off."

The A's repeated the error in the seventh when Jimmy Sexton drew back his bat and failed to make contact on his bunt attempt. Davey Lopes had to turn around halfway to home. Nolan got the putout on him, too.

The victory improved the Orioles' record in one-run games to 11-13.