Len Matuszek had a two-run double in a four-run third inning and George Bell and Ernie Whitt homered in a four-run fifth as the Blue Jays beat the Detroit Tigers, 9-2, last night in Toronto.

A crowd of 42,455, the largest to see a single night game at Exhibition Stadium, watched the American League East-leading Blue Jays win their 15th in 17 games and open an 8 1/2-game lead over Detroit. The Tigers have lost eight of their last 11, including the first two meetings in this four-game series.

Winner Dave Stieb (6-4) pitched a two-hit shutout over six innings, dropping his earned run average to 2.26, before being relieved by Dennis Lamp. Toronto's pitching staff set a team mark with 28 consecutive scoreless innings before Lamp gave up Lou Whitaker's RBI double and Kirk Gibson's sacrifice fly in the eighth.

With Toronto ahead by 1-0, Tony Fernandez started the third-inning rally with a double. Gibson's relay from right field to second skipped past shortstop Alan Trammell, who was charged with an error, and Fernandez advanced to third base. Two outs later, Lloyd Moseby singled, Willie Upshaw singled and Matuszek doubled for a 5-0 lead.

In the fifth, Upshaw led off with a walk and Bell hit his 11th homer of the season. Whitt homered for an 8-0 lead, finishing starter Walt Terrell (6-2). Whitt, a Detroit native, has hit 17 career homers against the Tigers (compared to four or less against every other AL team).