NASCAR Racing: History of Pit stops - time it takes, air wrenches, tire pit

Question
I want to find out how long the typical pit stop used to be 20 and 30 years ago.  I know that using process improvement and lean concepts, they have been able to reduce it to about 13 seconds on average today.

Answer
In the 70's the regular 4 tire pit stop averaged in the upper 20's to 30 seconds, in the 80's they had cut it down to the 18-20 second average, bringing dow to the lower teens by the end of the 80's. The two biggest changes were the high speed air wrenches and the quick pump jack (went from 3-4 pumps to get the car off the ground to 1-2 pumps).