the torsion bars are like a big spring, if you crank the bolt all the way up the key twists the bar the bar twists and pushes the control arm down which forces the the tire down into the ground. trust me, if you go to a truck pull watch the how a truck with the torsion bars all the way down. the front tires just spin out on the dirt not digging at all. a truck set up as with the bars cranked will pull with the front axles and will dig into the dirt. i know this works i have done it on mine, all the way down and slowly started to crank the bolts back up till we were happy!
there are so many threads you read about there being some standard rules for sled pulling 3 gear, 4 lo, torsion bars all the way down... there are so many things people could do to improve there trucks, one must think outside the box. one thing that helped me alot was gears, nobody ever thinks of those. with my truck suspension setup right and gears i can pull 4th gear with my stock charger making 28 psi and run with many trucks with alot more power.