Helio Castroneves regained his early season IRL IndyCar Series points lead thanks to victory in Sunday's rain delayed Firestone Indy 400 at the Michigan International Speedway.

After waiting more than two and a half hours while track officials attempted to dry the racing surface following early afternoon rain, pole sitter Castroneves went on to lead 61 of 200 laps for his fourth win of the season.

Coupled with his own success, poor results for erstwhile series leader Sam Hornish Jr and second place driver in points Scott Dixon helped catapult the cheery Brazilian back into the series lead with just three races remaining this year.

Once the track had been dried and racing had started Castroneves ceded the lead to his Marlboro Team Penske teammate Sam Hornish Jr before rare mechanical problems struck the defending Indy 500 winner shortly after one-quarter distance.

With Hornish Jr dropping out of contention, the only caution period of the race waved to allow the out-of-fuel Marty Roth to be towed back to the pits, which in turn gave everybody the chance to pit and handed the lead to Panther Racing's Vitor Meira, Vision Racing's Tomas Scheckter and Target Chip Ganassi Racing's Dan Wheldon for the remainder of the first 100 laps.

Castroneves didn't regain top spot until lap 134, by which time Scott Dixon had also seen his chances of victory disappear with a fuel starvation issue that left him two laps off the lead and while there would be no caution periods to bunch the field back up, the wide open nature of the two-mile Michigan oval still allowed for several more lead changes in the final quarter of the race.

Meira, Wheldon and Scheckter cycled through the lead one more time before Castroneves finally wrestled top spot away from Scheckter on lap 177, eventually opening out a two second advantage over second place finisher Vitor Meira by the time the chequered flag fell.

With only the one caution period during the event the race was run at an average speed of more than 193mph and with his fourth win of the year Castroneves now holds an eight point advantage over his teammate Hornish Jr in the IRL standings.

Meira's seventh career runner-up finish kept his title chances alive and he now sits fifth in points just 56 behind Castroneves while third place finisher Wheldon is now third in points too, 17 markers behind Castroneves.

Tony Kanaan kept his feint title chances alive with a fourth place finish while Scheckter completed the top five. Scott Sharp and Ed Carpenter were the only other lead lap finishers in sixth and seventh while rookie Marco Andretti, Kosuke Matsuura and rookie Jeff Simmons completed the top ten.

Defending Michigan winner Bryan Herta could only finish eleventh with Dario Franchitti 12th and the delayed Scott Dixon and Danica Patrick 16th and 17th respectively.

Hornish Jr was the only retirement of the race and thus scored minimum points for 19th and last place.