Helio Castroneves was impossible to stop on Saturday, converting his earlier track record-setting blistering pace in the heats qualifying session to a dominating performance in Heat 3 to win him provisional pole on the grid for Sunday's Iowa Corn Indy 250 presented by DEKALB at Iowa Speedway.

Earlier, Scott Dixon and Takuma Sato emerged one and two in the largely processional Heat 1, which allowed them to take part in the 'pole shootout' third heat as reward. Dixon's success was in stark contrast to his team mate Dario Franchitti who finished a lap off the leaders and gets a grid position near the back for the main race as a result.

In a rather more entertaining Heat 2, Graham Rahal emerged victorious after being made to work for it, coming through the field in thrilling fashion to take the lead from Ed Carpenter with four laps to go, with both men progressing to the pole shootout heat as reward when the race ended prematurely for James Jakes hitting the wall on lap 48.

Heat 1 results

1. #9 Scott Dixon Ganassi Honda 50 laps
2. #14 Takuma Sato AJ Foyt Honda + 0.7768s
3. #98 Alex Tagliani BHA Honda + 2.2856s
4. #1 Ryan Hunter-Reay Andretti Chevrolet + 2.6547s
5. #67 Josef Newgarden SFHR Honda + 1 laps
6. #18 Ana Beatriz Dale Coyne Honda + 1 laps
7. #6 Sebastian Saavedra Dragon Chevrolet + 1 laps
8. #7 Sebastien Bourdais Dragon Chevrolet + 1 laps
9. #10 Dario Franchitti Ganassi Honda + 1 laps

Heat 2 results

1. #15 Graham Rahal RLL Honda 50 laps
2. #20 Ed Carpenter Ed Carpenter Chevrolet + 0.5428s
3. #77 Simon Pagenaud Schmidt Honda + 2.1748s
4. #19 Justin Wilson Dale Coyne Honda + 3.998s
5. #55 Tristan Vautier Schmidt Honda + 16.5997s
6. #83 Charlie Kimball Ganassi Honda + 17.4519s
7. #5 EJ Viso Andretti-HVM Chevrolet + 1 laps
8. #16 James Jakes RLL Honda + 2 laps Accident
9. #78 Simona de Silvestro KV Racing Chevrolet + 3 laps

Heat 3 results

1. #3 Helio Castroneves Penske Chevrolet 50 laps
2. #12 Will Power Penske Chevrolet + 3.148s
3. #27 James Hinchcliffe Andretti Chevrolet + 4.439s
4. #25 Marco Andretti Andretti Chevrolet + 4.9046s
5. #9 Scott Dixon Ganassi Honda + 6.5829s
6. #20 Ed Carpenter Ed Carpenter Chevrolet + 8.3003s
7. #14 Takuma Sato AJ Foyt Honda + 11.295s
8. #11 Tony Kanaan KV Racing Chevrolet + 16.0737s
9. #15 Graham Rahal RLL Honda + 1 laps
10. #4 Oriol Servi? Panther Chevrolet + 1 laps