I guess now that I should have included a bit of other info in the original post. As of now, I own 3.25, 3.07. 3.00, 2.94, 2.91, 2.86. 2.80, 2.75, 2.50 and 2.47 gear sets for a Ford 9"....... a few of them in duplicate.
I appreciate you all wanting to help me out but the way this is working for me is that I have been "tuning" the final drive gear ratio in about 1 - 2% increments over the last few meets. I am now using the 2.80 set in the car. I did not get to drive it to its maximum potential with those gears (we got rained and probably snowed out at the W/Fs last year), so the 2.80s will be in the car until at least mid week of Speedweek this year while we tweak the carburetor a bit. We are running the engine up to 200 to 250 rpm past peak horsepower at about 8950 rpm to just over 9000 rpm in the terminal velocity area at the end of mile 5 (redline is theoretically 9400 rpm but it doesn't seem to want to go there). We do know that the tires are growing some (about 1.6%+/-) because we are about 150 rpms lower than mathematical calculations say the rpm should be at that speed. The kicker is that we had a bigger carb that had not been dyno'd on the engine. We played with tuning on it for 3 runs and then we put the smaller carb back on and picked up a few miles per hour - but not enough! That is when we started going to taller gearing and we kept picking up speed - finally qualifying for the record - and then going 1.5 mph faster than the qualifying speed on the return run, which was on the Friday morning of Speedweek and the air was the densest it had been all week.... We also had a front tire that went flat on that run and I know THAT had a cost of several miles per hour.
With all that in mind, we are probably in the "ballpark" to go over 280 (perhaps up to 285) mph with the present combination. After that, the last realistic gear ratio change for the car will be the 2.75s which should theoretically give the car another 5 mph..... Now, here is my logic on what I have presented so far- Do I, if I have achieved 290 mph, look at everyone and say, "That's it.... we can't go any faster." .... and then we pack up and go home.....
See, this is Bonneviile Landspeed Racing and until the next gear ratio change shows the car as slowing down 'cuz it can't pull the gear, how does one know that the limit has been achieved?