This is the best explanation I could come up with. Hopefully this will help.
Here is NASCAR’s explanation on how it works. Still waiting for the lineups for the 150s.
Qualifying
• One round of NASCAR Sprint Cup Series timed qualifying will be held. Each team may run two laps with the fast lap setting the qualifying time. The two fastest qualifiers set starting positions one and two and are the only guaranteed positions, filling the front row for the Daytona 500.
• The Gatorade Duels, the 150-mile qualifying races, will determine starting positions for the Daytona 500 beyond the front row. In the event of cancellation, the field will be set according to the NASCAR Sprint Cup Series Rule Book.
Gatorade Duel Assignment
• The eligible highest ranked 35 in 2008 car owner points will be assigned to Gatorade Duel races based on their standing in the 2008 final car owner points. Odd-numbered owner points will compete in the first Gatorade Duel; evennumbered owners will compete in the second. The only exception is that the fastest qualifier will start on the pole in the first Gatorade Duel and the second fastest will start on the pole in the second, regardless of 2008 car owner point standings.
• Owners who failed to finish in the top 35 of the 2008 car owner points will be assigned to a Gatorade Duel based on qualifying times – the highest qualifying owner to the first Duel; the next to the second and alternating through the remaining entries. Starting positions for the Gatorade Duels are based on qualifying times.
Daytona 500 Lineup
• Finishing positions in the Gatorade Duels will determine starting positions in the Daytona 500 once the two fastest qualifiers will start on the front row of the Daytona 500 based on their qualifying times, regardless of their finish in the Duels. Based on their finish in the first Duel, the eligible highest ranked 35 in car owner points plus the two highest finishing non-top 35 teams will be lined up in the odd-number starting positions. Based on their finish in the second Duel, the eligible highest ranked 35 in car owner points plus the two highest finishing non-top 35 teams will be lined up in the even-number starting positions.
• The remaining positions will be filled based on qualifying times beginning with the next available position.
• The composition of the front row will reduce the above numbers. If there are top-35 teams on the front row, the number of guaranteed starters is reduced accordingly. If there are no top-35 teams on the front row, the number of cars that get in based on time are reduced accordingly.
• The 43rd starting position will be assigned to any car owner who has the most recent eligible past NASCAR Sprint Cup champion as long as the past champion competed in the 2008 NASCAR Sprint Cup season. If the 43rd position is not used by a past champion, it will be assigned to the next highest qualifying time.
Here is NASCAR’s explanation on how it works. Still waiting for the lineups for the 150s.
Qualifying
• One round of NASCAR Sprint Cup Series timed qualifying will be held. Each team may run two laps with the fast lap setting the qualifying time. The two fastest qualifiers set starting positions one and two and are the only guaranteed positions, filling the front row for the Daytona 500.
• The Gatorade Duels, the 150-mile qualifying races, will determine starting positions for the Daytona 500 beyond the front row. In the event of cancellation, the field will be set according to the NASCAR Sprint Cup Series Rule Book.
Gatorade Duel Assignment
• The eligible highest ranked 35 in 2008 car owner points will be assigned to Gatorade Duel races based on their standing in the 2008 final car owner points. Odd-numbered owner points will compete in the first Gatorade Duel; evennumbered owners will compete in the second. The only exception is that the fastest qualifier will start on the pole in the first Gatorade Duel and the second fastest will start on the pole in the second, regardless of 2008 car owner point standings.
• Owners who failed to finish in the top 35 of the 2008 car owner points will be assigned to a Gatorade Duel based on qualifying times – the highest qualifying owner to the first Duel; the next to the second and alternating through the remaining entries. Starting positions for the Gatorade Duels are based on qualifying times.
Daytona 500 Lineup
• Finishing positions in the Gatorade Duels will determine starting positions in the Daytona 500 once the two fastest qualifiers will start on the front row of the Daytona 500 based on their qualifying times, regardless of their finish in the Duels. Based on their finish in the first Duel, the eligible highest ranked 35 in car owner points plus the two highest finishing non-top 35 teams will be lined up in the odd-number starting positions. Based on their finish in the second Duel, the eligible highest ranked 35 in car owner points plus the two highest finishing non-top 35 teams will be lined up in the even-number starting positions.
• The remaining positions will be filled based on qualifying times beginning with the next available position.
• The composition of the front row will reduce the above numbers. If there are top-35 teams on the front row, the number of guaranteed starters is reduced accordingly. If there are no top-35 teams on the front row, the number of cars that get in based on time are reduced accordingly.
• The 43rd starting position will be assigned to any car owner who has the most recent eligible past NASCAR Sprint Cup champion as long as the past champion competed in the 2008 NASCAR Sprint Cup season. If the 43rd position is not used by a past champion, it will be assigned to the next highest qualifying time.
