As long as you have to speed then you have the potential to put up a good time. Its all about your get off, its those first 3 steps off the line. Its hard to explain the proper technique in words it has to be shown but at my school we have trainers who would help us out with our technique in the 40 yard dash. As long as you are an athlete and have good speed then all that matters is those first five yards of the dash, get that down and youll put up a good time.