Ken Singleton's eighth-inning single prevented Cleveland right-hander John Denny from pitching his fourth straight shutout tonight. It was small consolation for the Baltimore Orioles.

The Indians' aggressive base running and Denny's 10-strikeout pitching were the keys to a 4-1 Cleveland victory that further tightened the crowded American League East race. The Orioles and Milwaukee Brewers are now two games out. The Indians, in sixth place, are three games behind front-running Detroit with 24 days left.

The Indians are a second-season contender if Denny and Bert Blyleven, Wednesday's winner, keep pitching the way they have. Tonight the 6-foot-3 Denny had struck out every man in the Orioles' starting lineup by the end of the fifth inning. His 10 strikeouts were a career high and it was only a stiff elbow that terminated his shutout streak after 34 innings.

Rick Dempsey opened the eighth with a single, the first hit off Denny since the second inning. Al Bumbry forced Dempsey, took second on Rich Dauer's infield out and scored on Singleton's single to right. That not only ended Denny's scoreless streak, it took him out of the game with Murray at the plate as the tying run.

Dan Spillner took over and walked Murray. Then Terry Crowley sent a long drive to left center that was brought in by Rick Manning on the run at the warning track.

Denny, who has won five in a row, was so effective that plate umpire Jim McKean told Cleveland Manager Dave Garcia, "He really had great stuff." With four called third strikes in the first three innings, some of the Orioles doubted whether McKean could see some of it, and he and Manager Earl Weaver had a brief shouting match in the fifth.

Right-hander Sammy Stewart allowed only six hits in seven innings, but the Indians made the most of them with excellent base running.

Jorge Orta singled to start the fourth and broke for second on a hit and run. He came to a stop near second as center fielder Bumbry had a chance to catch Mike Hargrove's liner, but when it fell a hop in front, Orta accelerated once more and made it to third. The extra base was crucial as Orta scored on Toby Harrah's sacrifice fly.

In the sixth, Manning lined a seemingly routine single to right center, but kept on going and beat Bumbry's on-target but weak throw to second. Long flies by Orta and Hargrove made it 2-0, the extra base again decisive.

A double by Von Hayes and a single by Pat Kelly, both left-handed batters going to the opposite field, boosted the margin to 3-0 in the seventh. A single by Harrah, a sacrifice, an infield out and reliever Tippy Martinez' wild pitch provided an insurance run in the ninth.