He was quickly into third chasing Dahm and Mt Maunganui's Bradley Tyrrell before a classic high and low groove sprint car duel with Dahm developed.
"It was a great track tonight," said Murphy. "It opened up so you race a high line or run around the bottom."
He chose the shorter way around and Dahm was flying out wide near the wall.
"I remembered him [Dahm] from last year. He was driving very well," said Murphy. "I wasn't sure if I could actually get him on the bottom but I knew if I kept showing my nose I might force him into a mistake."
Dahm lost his momentum when his right front wheel glanced off the front straight wall and Murphy seized the lead soon after. Two laps from the finish Dahm ran out of fuel and Murphy was nearly half a lap clear at the finish with Tauranga's Rodney Wood getting the better of Tyrrell in the battle for second.
It was the first of at least three Baypark appearances this summer for Murphy who is gearing up for the NZ title at Western Springs in early January.
He and regular crew chief Chris Atkinson arrived last week and rebuilt the Dalton's team car with some new components. Murphy has now returned to California for the awards banquet for the "King of the West" sprint car series which is next weekend - he finished fourth in the series which was won by another regular New Zealand tourist Jonathan Allard - and will be back at Baypark on November 17.
He says having his regular fulltime crewman with him for his third New Zealand summer campaign will be an advantage. "Chris started working for me this year and we've had a good year together. He'll be able to quarter-back the guys on the Dalton's team and I'll be able to concentrate on driving."