Mike Barnes blocked a 27-yard field goal attempt by Jim Turner with eight seconds left in the game yesterday to preserve a 7-6 Baltimore Colt victory over the defending AFC champion Denver Broncos at Memorial Stadium.

Barnes broke through the middle of the line to thwart a last-ditch effort by the Broncos, who had marched from their 44 in the last 1:42 of the game. Denver quarterback Craig Morton had passed 18 yards to Jack Dolbin and 22 to Riley Odoms on the first two plays of the drive, following Rick Upchurch's 15-yard punt return.

The Colts used a big-play defense to hand the Broncos their third loss in eight games. The victory upped Baltimore's record to 3-5.

The Broncos outgained the Colts, 353-260 in total yards, but could not penetrate the end zone, settling for two field goals by Turner. All the scoring was in the first half.

The Colts came into the game bragging but the Broncos nontheless drove from their 30 to the Baltimore 26 on the first series. But Turner's 43-yard field-goal attempt was short. short.

Baltimore could get little going offensively, losing a yard on six plays during their first two possessions.

Denver got on the board when Turner's 33-yard field goal with 3:49 left in the first quarter culminated a 10-play, 38-yard drive.

Bill Troup, Baltimore's backup quarterback who started in place of the injured Bert Jones, suffered a broken left hand late in the game and will be sidelined at least four weeks.

A Colt spokesman said Troup broke three bones in his nonthrowing hand, which was placed in a cast after the game. If Jones is not able to play, Mike Kirkland will be the only healthy Baltimore quarterback for Sunday's game at Miami.

Troup silenced the boos of the Memorial Stadium fans by taking to the air early in the second period. Starting on his own four, Troup completed four of five passes, including a 39-yarder to Roger Carr.

On third and 5 on the Bronco 19, Troup rifled a pass toward Glenn Doughty poised in the middle of the end zone. A Denver defender got a hand on the pass and tipped it into Doughty's waiting hands for a 7-3 Colt lead with 7:41 left in the half.

Denver made it 7-6 following a 14-yrad return of an interception by linebacker Godwin Turk. After the Colts held Denver to six yards on three plays from the Colt 15, Turner booted a 26-yard field goal 47 seconds before the end of the half.

The Colts got a big break early in the third quarter after the Broncos had driven 55 yards to Baltimore's 28.. On third and 10, defensive tackle Joe Ehrmann hit Morton while the quarterback was attempting to pass. Morton fumbled and end Fred Cook of Baltimore recovered.

Troup apparently injured his left arm with 5:03 left in the game when he was hit on a short run. Mike Kirkland came in to finish the game.

A 36-yard punt return by Rick Upchurch gave the Broncos the balll on their own 45 with less than five minutes remaining. But a holding penalty against the Broncos and a gang-sack of Morton by three Colts stopped the drive.

Troup injured his hand with 5:03 left in the game, when he was hit on a short run. Kirkland came in to finish the game.

A 36-yard punt return up Upchurch gave the Broncos the ball on their own 45 with less than five minutes left. But a holding penalty against Denver and a sack of Morton by three Colts stopped the drive.