Do I need 4.88s?!

Current set up goes through the lights at 7000 rpm with 4.56 gears at 145mph with 33" Goodyears. Engine made peak HP at 7300 on the dyno and I shift at 7500. I need new slicks for next season and was thinking of some wide 14x32's but I dont think there will be enough difference in rollout to change what it traps at. My converter is an ATI 9" that flashes at 5800. My inner voice tells me to try the slicks and go from there, but I was looking for some opinions. I also plan on installing a hood scoop before next season so I know I'll have some retuning also.
I just have a hard time believing a 540 needs 4.88's to get down the track optimally.
Thanks,
Tony

Basically you are wasting the last 600 rpm's of your
power.... you make peak power at 7300 and in MOST
cases you want to cross the line at 10% above peak HP
but you also need to look at the drop back RPM on the
shifts.. so if its falling down past peak torque its
most likely hurting the ET

As far as tire hieght making a RPM differece at the finish line my Duster crooses the finish line at 7000 RPM at 134.4 MPH with a set of M/T 315x60x15 ET Street radials (94 inch circumference) and crosses at 6500 RPM at 134.6 MPH with a set of M/T 10.5x31x15 W bias plys, very near the same ET also I would definetly try the tires first, maybe a set of radials in that size

short shift 1st gear at 6200 first, see what happens with et

I have 4.56's and 10.5W-31's w/ 727 auto.

I shift such that it goes into second at 7,300 rpm and into 3rd at 7,600 rpm and it traps as high as 8,100 rpm.

Peak power on Dyno was at 7,200 rpm.

If i wind it higher in first say to 7,800 rpm before the shift actually happens, I lose .05 easy...

I would keep the bigger tire and go with the 4.88's first. All the ET has happened by 1,000 feet IMO.

Good luck with it!

MT 14x32, 5600 stall, 4.88 rear gear, shift at 7000, cross the line at 7200 @ 142mph 9.4 e.t

The quickest ETs are usually achieved by gearing for cross rpm.

This is why dyno numbers PAST peak are important. If horsepower hangs on well past peak you can get more agressive with converter flash and gearing. Obviously, the opposite is true if a combination drops like a rock after peak.

I'd say try the .88s......at least.

All the testing I've done over the years, my cars have always liked to trap 300 RPM's over the best shift point.
I shifted my 340 Scamp at 6700, trapped at 7000.
Shifted my 451 DartSport at 6300, trapped at 6600.
69 Dart 500" shifted at 6600, trapped at 6900.

I would try the shorter tire which should pick you up about 300 rpm. With the overly aggressive first gear in a 540/Torqueflite combo (assuming you run one!) you might lose on the bottom what you pick up at the stripe. What was peak torque on the dyno sheet? 5800 rpm might be a tad low, and a converter loosened up to gain 400 stall may put you up around 7600 rpm with a 102 roll out and 4.56 gears. Mine gained 300 rpm on top when loosened up.

I would try the shorter tire which should pick you up about 300 rpm. With the overly aggressive first gear in a 540/Torqueflite combo (assuming you run one!) you might lose on the bottom what you pick up at the stripe. What was peak torque on the dyno sheet? 5800 rpm might be a tad low, and a converter loosened up to gain 400 stall may put you up around 7600 rpm with a 102 roll out and 4.56 gears. Mine gained 300 rpm on top when loosened up.

This was in the back of my mind too Greg and yes its a 727.Peak torque was 5800rpm. The ATI conv is very tight 4% if I figured it correctly?