Dungey, the KTM rider from Belle Plaine, Minn., has 14 career 450SX victories. He moved into second place in the standings, 23 points behind three-time defending series champion Ryan Villopoto.
"We needed that win, it's been a long season," Dungey said. "The track got really torn up tonight. ...I got up front pretty early and was able to hold a good pace, and not do anything stupid. It was one of the toughest races of the season for sure. We have to keep taking (the championship) one race at a time. It's a great series with a lot of good riders so you have to just keep plugging away."
Cole Seely was third, followed by Villopoto and Broc Tickle.
Adam Cianciarulo won the 250SX race for his second victory in the first three races of the Eastern Regional season. Kawasaki teammate Martin Davalos was second, followed by Justin Bogle and Matt Bisceglia.
"I'm definitely happy with my ride. It was more of a smart race for me," the 17-year-old Cianciarulo said. "I knew the whoops would be key because they really deteriorated. I had a couple close calls early on, but was able to keep it close to Martin. He made a mistake and I was able to capitalize on it. I almost gave it back a little bit later, but I got back on the bike quick and kept the lead."
Cianciarulo, from Port Orange, Fla.