Well, lets just say I hit a 13.50 now. I will say 2 tenths for a 1/2 turn of the drive shaft is more than a reasonable expectation (2.76 to 3.23's). I know I can get 3 tenths from heads. That, my friend, would be a 12.99 on a good pass. What about if I gain a little more, and my car is already a 13.40 ? Now you are looking at 12.8's ??