The Washington Capitals exploded for four third-period goals to defeat the Pittsburgh Penguins, 4-2, in an exhibition game tonight.

The Capitals showed little offense through the first two periods, but they caught fire after Guy Charron's eight-foot shot on a power play at 2:28 of the third period tied the score at 1-1.

Thirty-three seconds later, Gerry Meehan beat Penguin goaltender Denis Herron on a breakaway and, from then on, the Capitals dominated. Ace Bailey said a loose puck into an empty net vacated by Herron at 7:33, and Bob Sirols added another powerplay goal.

Sirols, alone at the right faceoff circle, fake da Penguin defenseman to the ice and then beat Herron.

Goaltending kept the Capitals in the game through the first two periods, as the Penguins outshot them, 27-17. Especially good was veteran Garry Smith, who made 19 saves through the first half of the game.

Penguin Blair Chapman scored the only goal against Smith, tipping in a blind shot on a powre play in the first period.

Rookie Tom Cassidy tucked a puck in from behind the net on goaltender Bernie Wolfe in the third period.

Capitals rookie Bob Picard and Chapman squared off for a fight after jockeying for position on a faceoff at center ice early in the second period. Picard dominated the fight until Penguin center Greg Malone jumped in. Malone was ejected as the third man in.

The Capitals raised their preseason record to 2-4-1 and avenged an eariler 2-1 loss to the Penguins. The Penguins, 4-3 in preseason, play their Norris Division rivals Friday at Capital Centre.