Doug Betters deflected a conversion kick by Philadelphia's Paul McFadden to give the Miami Dolphins a 24-23 victory today and extend their record to 11-0, the second best start in National Football League history.

Betters, a 6-foot-7 defensive end, said he had broken through the Eagles' soft spot he noticed in long hours of watching films and barely tipped McFadden's first extra-point kick in the game. He went through the same hole for his block with 1:52 left.

"We've been working on this," he said. "We saw that No. 64 (Dean Miraldi) had a weakness.

"Three or four guys wedged together to open the lane for me. I caught it right on my fingertips. It wasn't much, but it was enough . . ."

Philadephia Coach Marion Campbell said he was concentrating on preparing the defense for the final two minutes when he looked up and saw the block.

"I thought it was going into overtime, to be honest," Campbell said. "We played so hard and lost, and that hurts more because of the work our guys put into it."

The Dolphins, who had trailed only three times all season, were behind more than three quarters against the Eagles, then scored two touchdowns in 3:44 bridging the third and fourth periods to take a 21-17 lead.

Uwe von Schamann's 27-yard field goal made it 24-17, but the Eagles drove right back downfield with Ron Jaworski's 38-yard pass to Melvin Hoover giving the Eagles a touchdown and a chance to tie on the extra point with 2:35 left.

But Betters foiled McFadden.

The Eagles (4-6-1) kept Miami's high-powered offense off the field by unexpectedly running for 117 yards the first half.

But Miami quarterback Dan Marino started to connect in the second half, passing for 13, 14, 18, 9 and 12 yards on a 68-yard march that ended in Woody Bennett's two-yard scoring run with 2:07 left in the third quarter.

That left the Dolphins behind, 17-14, but they went ahead when Paul Lankford, beaten on the Eagles' first touchdown, intercepted Jaworski at the Eagles' 26 on the next play from scrimmage. Seven plays later, Pete Johnson scored from a yard out to put Miami ahead, 21-17.

The Eagles astounded the Orange Bowl crowd of 70,223 by plowing through Miami's defense on drives of 80 and 63 yards in the first quarter.

Philadelphia, the worst running team in the NFL with an average of 77 yards a game coming in, manhandled the Dolphins for 85 yards on 16 carries. Jaworski ended each of the run-dominated drives with medium-range scoring passes.

First he looped a 19-yarder to Mike Quick with 10:35 left in the quarter, then he threw a 13-yarder to Tony Woodruff with 2:34 to go.

Marino's 11-yard line drive to Nathan with 1:18 left in the half made it 14-7. Miami had threatened earlier in the quarter, but on third and fourth downs inside the one, Johnson failed to score and the Dolphins lost the ball.

The Eagles moved 57 yards in another grind-it-out drive on their first possession of the second half. Michael Haddix, subbing for Wilbert Montgomery, who injured his hamstring, ran for 21 yards on the key play of the march.

But Haddix was stopped short on third and two at the Miami 29, and McFadden kicked a 45-yard field goal for a 17-7 lead.

Then it was all Dolphins until the Eagles got the ball with 4:31 left and trailing 24-17.