Davel.,I too questioned the 6k force, but I had no frame of reference. What I did know is the funny car that took flight weighted over 2,300 lbs. and the headers were not pointed straight down after the ends burned off, so there was a vector involved. Using the 4 tires spring rates and the change in ride height data that would also suggest the the thrust wasn't in the 6k range but maybe 1/2 that amount. But again the header angle during the test still had a vector component, the pipes where not pointing straight up. Another effect of header thrust with these cars is if one cylinder goes out it is very difficult for the driver to keep the car going straight. Bottom line is there is a great deal of thrust, after laying the headers back from the original position the cars picked up a significant performance gain.