PHILADELPHIA (AP) -- Kyle Korver's role has changed. The big 3-pointers he has a timely knack of hitting have stayed the same.
The near-perfect sharpshooter used his 3s to help bump Philadelphia to an even bigger 3: 3-0 for the first time in six seasons.
Andre Iguodala scored 20 points for the surprising Sixers, who are the only undefeated team in the Eastern Conference.
"We've got to keep on building on what we've been doing," said Korver, who hit 5 of 6 3-pointers. "We have a long ways to go, but we feel like we're doing OK right now."
Korver rallied the Sixers with 3s in the third quarter and helped them build a 17-point lead midway through the fourth until Walker cut the gap with a 3-point rampage of his own.
Walker sank three straight 3s that made it a 10-point 76ers' lead late in the fourth.
Unlike last season, when the Sixers had a troubling habit of folding down the stretch, this year's team has shown a dogged resolve to keep the lead. Iguodala, who had a sensational all-around game, hit an 18-footer and Kevin Ollie made a baseline jumper to push the lead back to 13, and the Sixers held on for their most impressive victory of the season.
The Heat played without center Shaquille O'Neal, who bruised his left knee in Friday's win at New Jersey. O'Neal is day-to-day.
Riley said O'Neal would have X-rays when the team returned to Miami.
"Not having Shaq changed our whole game plan," coach Pat Riley said. "We were a little surprised that prior to the game we found out he wasn't going to play."
Shaq would have made little difference against Korver. The former starter has found his niche this season off the bench, hitting clutch shots with such frequency that his minutes haven't really been affected.
Korver got hot in the third, sinking three 3-pointers to extend his streak to nine straight overall going back to Friday's win in Orlando. The streak ended when he missed a baseline attempt in the fourth.
"He has to be that sparkplug off the bench," Iverson said. "We're going to need Kyle to do a lot of things for us throughout the season. It's great how he handled the responsibility of being the sixth man."
After getting pounded on the boards in the first half, even with O'Neal gone and Alonzo Mourning battling foul trouble, the Sixers came out with a renewed zest in the second half.
Iverson and Korver hit consecutive 3s that sliced the deficit to three, then Korver added two more 3-pointers that tied the score at 71.
Korver added a jumper and a couple of free throws before the quarter was over to stretch the lead to 78-73.
"Shooting 3s is always going to be what I do best," Korver said. "It better be what I do best."
Iguodala hit a pair of 3s in the fourth that electrified the crowd and gave the Sixers a needed cushion to withstand Walker's late hot streak.
Philadelphia had 26 assists and only eight turnovers. They also outrebounded the Heat, 43-40.
Chris Webber had 11 of those rebounds for the Sixers, including six in the third, but continues to slump from the floor, with a 5-for-13 effort for 10 points. He was benched for the entire fourth quarter.
Starting center Samuel Dalembert also was held out of the fourth and Korver was scoreless.
Webber deftly deflected numerous questions about his benching, smiling through brief answers and saying he was happy the Sixers were 3-0.
"It's whatever," he said.
Mourning struggled filling in for O'Neal, picking up his fourth foul early in the second quarter and was a non-factor with six points. Dorrell Wright set a career high with nine rebounds, but had none in the third when the Sixers outrebounded the Heat 13-7.
"We hurt ourselves out there," Mourning said. "We didn't do anything to alter their play down the stretch. We let them get into a comfort level."
Now the Sixers seem quite comfortable sitting atop the East.
Iverson was hit with a technical foul in the first quarter. ... Iverson was tripped hard by Mourning in the fourth, and a clear path foul was called. Iverson sank both free throws. ... The Sixers won their first 10 games in 2000-01 and advanced to the NBA Finals.