The bottom bar should NEVER be level in the car. If you read the Doorslammers book Morgan says to make it level, but he corrected this, in print, in about 2002 or 2003. The bottom bar should run down hill, in its middle holes, to intersect and run through the front ball joint.
If you do that, you have kicked about 90% of the ***. The rest depends on HP, RPM and how hard you want or need to hit the tire. If you are making over 500 HP and using a trans brake or better yet, you have a stick, I would start with an IC, at the MINIMUM of 100 inches out, and about 6-8 inches up from the ground. Then you have to tune from there.
Never EVER have the bottom bar parallel to the ground.
My last race car was a small block stick, I shifted at 8500. My IC was either 104 or 108 out and 4-6 inches up. I have done BB stick cars that were 115 inches out and -2 inches down. You are using chassis to control how hard the tire gets hit.
