You should be able to score a 13 sec time slip with that 318, mostly a matter of timing and dialing everything in correctly. When you go to the strip, have a notebook and keep detailed records of EVERYTHING that changes from run to run and from week to week, including carb jetting, tire pressure, starting line technique, etc. Sometimes you end up going backwards and can't quite figure out why, and the notebook takes the guess work out of the equation. I know what you mean about the heigh problem, my track is a little over 2800 feet altitude. Keep poking at it and you'll get there. :)
