Joe Lefebvre singled home Willie Hernandez with two out in the 13th inning tonight to give the Philadelphia Phillies a 4-3 victory over the Pittsburgh Pirates.

The victory, coupled with Montreal's 5-4 loss in New York, gave the Phillies a half-game lead over the Expos in the National League East. St. Louis trails by one game; the Pirates, having lost five of their last six, are 1 1/2 back.

Hernandez singled off the ankle of losing pitcher Jim Bibby (4-12) with two out, went to second when Mike Schmidt walked and to third on Bibby's wild pitch. Lefebvre's hit on a 1-2 pitch scored Hernandez.

Hernandez (6-4), who pitched three hitless innings, has six hits in 13 at bats this season and is hitting .461. "I was just trying to get on base any way I could," he said.

The Pirates tied at 3 in the eighth on bases-empty homers by Dave Parker and Tony Pena off starter Steve Carlton, who is seeking his 298th victory in the majors but hasn't won in his last five starts, losing four.

Parker, leading off the inning, hit a 1-1 pitch into the seats in right for his 11th homer. One out later, Pena hit a 1-1 pitch over the fence in left for his 11th homer. Gene Tenace doubled, chasing Carlton, but Al Holland got the next two batters.

The Pirates took a 1-0 lead in the fourth on a leadoff homer by Jim Morrison.

Pirates starter John Candelaria pitched a perfect game through five innings but in the sixth hit leadoff batter Bo Diaz with a pitch. One out later, Carlton forced Diaz at second. Joe Morgan grounded to third baseman Morrison, whose wild throw to first pulled Tenace off the bag and Carlton took third. Pete Rose's single made it 1-1.

The Phillies took a 3-1 lead in the seventh. Schmidt singled but was forced at second by Sixto Lezcano. One out later, Garry Maddox singled Lezcano to third and Lezcano scored on Diaz's single, Maddox on Ivan DeJesus' double.