I've been racing at an 1/8th mile track, car is pretty much right where I want it as in Sportsman class (NHRA ET racing) you cannot dial quicker than 7.50 . Bad air gets the car into 7.8's, it's run a couple 7.5's in the spring and last year at the finals in Brainerd it ran a 7.49 as part of one of its quarter mile passes. In the 1/4 you cannot dial under 12.00, and the car has run high 11.90's with a best of 11.86 in a time trial. This year when we hit the 1/4 mile I dialed back the distributor a few degrees and the car ran 12.02/12.04, right where it belongs.
With the "official" racing over, I decided to see what a gear change would do and swapped out the 4.30s for a 3.55 set. Much better for driving down the highway to the local track, and I figured the car would get right around 8.0s. A friend with a lot of experience racing Mopars guessed maybe 7.85's. Wouldn't you know, first run was a 7.504. When the day was done, and the headwinds died down, it ran a 7.48 best. Obviously we had good weather last weekend for this kind of performance (MPH was in the ballpark at 90 and change) and one other potential variable is that I did not check the timing after dialing it back to where I have it marked on the block and distributor housing. Could be a degree or two additional in it, it's marked for 34 total.
Details are, the car weighed 3540lbs on Topeka's scale, has S/S springs, and the motor's a typical build as in Chuck Senatore's Big Block Mopar book. 440 .030" over, Holley Street Dominator intake, Demon 750, ported iron 906s, 10.25:1 pistons at .005" down, Racer Brown SSH-44. Shifts at 5400 rpm according to the chip in the shift light. Manual valve body 727, 9.5" Dynamic converter.
I called Dynamic to tell this tale, and the estimation is that the 440 is getting into a somewhat better launch RPM as the converter sees a different loading from the gear ratio change. Could be what kept the 60' time in line with the times from the steeper gears. I'm just glad to have the lower highway RPMs and no change to the overall performance.
With the "official" racing over, I decided to see what a gear change would do and swapped out the 4.30s for a 3.55 set. Much better for driving down the highway to the local track, and I figured the car would get right around 8.0s. A friend with a lot of experience racing Mopars guessed maybe 7.85's. Wouldn't you know, first run was a 7.504. When the day was done, and the headwinds died down, it ran a 7.48 best. Obviously we had good weather last weekend for this kind of performance (MPH was in the ballpark at 90 and change) and one other potential variable is that I did not check the timing after dialing it back to where I have it marked on the block and distributor housing. Could be a degree or two additional in it, it's marked for 34 total.
Details are, the car weighed 3540lbs on Topeka's scale, has S/S springs, and the motor's a typical build as in Chuck Senatore's Big Block Mopar book. 440 .030" over, Holley Street Dominator intake, Demon 750, ported iron 906s, 10.25:1 pistons at .005" down, Racer Brown SSH-44. Shifts at 5400 rpm according to the chip in the shift light. Manual valve body 727, 9.5" Dynamic converter.
I called Dynamic to tell this tale, and the estimation is that the 440 is getting into a somewhat better launch RPM as the converter sees a different loading from the gear ratio change. Could be what kept the 60' time in line with the times from the steeper gears. I'm just glad to have the lower highway RPMs and no change to the overall performance.
