The first five runners took a combined total of 5*8 = <<5*8=40>>40 hours to finish the race.
The number of runners who finished the race 2 hours later after the first five is 8-5 = <<8-5=3>>3
The 3 runners who finished the race 2 hours later took a total of 8+2 =<<8+2=10>>10 hours to run the race.
Together, the three runners who finished the race in 10 hours took a total of 10*3 = <<10*3=30>>30 hours.
All eight runners took 30+40 = 70 hours altogether to finish the race.
#### 70