I accidently left in second gear with my Dart many years ago. BIG stroker (for the day!) The dial was 10.20, I ran 10.45 flat out. Loose converter though. A lot depends on that converter being loose enough to be high in the horsepower curve. If it isn,t that will really hurt ET. Leaving in 2nd was like my 4.10 gear turned into a 2.70!!