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Re: 3.55 vs 3.91 track time differences?
[Re: Jeff_383]
#3147470
05/29/23 06:46 PM
05/29/23 06:46 PM
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Joined: Jan 2003
Posts: 20,217
Park Forest, IL
slantzilla
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 20,217
Park Forest, IL
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Just a guess, you may not lose much ET, maybe .05, but will probably pick up a little MPH.
"Everybody funny, now you funny too."
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Re: 3.55 vs 3.91 track time differences?
[Re: Jeff_383]
#3147471
05/29/23 06:52 PM
05/29/23 06:52 PM
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Joined: Jan 2003
Posts: 31,078
Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,078
Oregon
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All else being equal, would there be a change in 1/4 mile times going from 3.91 to 3.55?
3900lb b body, large cube stroker, same PTC 9.5 converter (built for car with 3.91's) Can't really say without looking at the data log or some numbers. If the car is on the rev limiter going down the track then it might pick up time. If it is traction limited it might go quicker and faster with less gear. If the 3.91 gears are perfect for the engine and car then it will slow down.
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Re: 3.55 vs 3.91 track time differences?
[Re: AndyF]
#3147477
05/29/23 07:19 PM
05/29/23 07:19 PM
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Joined: Jan 2004
Posts: 878
Pittsburgh, Pa
Jeff_383
OP
super stock
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OP
super stock
Joined: Jan 2004
Posts: 878
Pittsburgh, Pa
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If the 3.91 gears are perfect for the engine and car then it will slow down.
I'm not really sure. The engine made 601 horsepower at 5500 and 633 torque at 4500
I know that's a vague answer, but I never really picked a gear to build on.
Last edited by Jeff_383; 05/29/23 07:36 PM.
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Re: 3.55 vs 3.91 track time differences?
[Re: Jeff_383]
#3147502
05/29/23 10:19 PM
05/29/23 10:19 PM
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Joined: Jan 2003
Posts: 21,546
N.E. OHIO, USA
A12
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 21,546
N.E. OHIO, USA
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All else being equal, would there be a change in 1/4 mile times going from 3.91 to 3.55?
3900lb b body, large cube stroker, same PTC 9.5 converter (built for car with 3.91's) What's the car running now with the 3.91?
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Re: 3.55 vs 3.91 track time differences?
[Re: topside]
#3147792
05/31/23 11:59 AM
05/31/23 11:59 AM
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Joined: Oct 2004
Posts: 2,843
Connecticut
FurryStump
master
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master
Joined: Oct 2004
Posts: 2,843
Connecticut
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Taller gear should raise the converter's stall speed a bit.
Whether the car wants that is hard to tell from here with the info so far. Flash rpm yes, stall no. Rear gear has no effect on stall and it really only changes flash rpm because of how flash rpm is defined, not a “real” change to the actual flash rpm. The change is the car just moves easier/sooner. So yes the rpm will be lower when the car first moves, but you can still get to the power band quicker during the run. (The reason we play with flash in the first place)I went with a low gear set 904 which would “lower” my flash rpm, but because the car is moving, I would get to peak torque .5 second quicker in the run, even with the “reduced” flash rpm.
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Re: 3.55 vs 3.91 track time differences?
[Re: Jeff_383]
#3147834
05/31/23 01:58 PM
05/31/23 01:58 PM
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Joined: Dec 2013
Posts: 4,704
Wichita
GY3
master
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master
Joined: Dec 2013
Posts: 4,704
Wichita
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Nothing with that combo.
We run a 3.54 gear with a 505" stroker and rear ratio seems to matter very little with the torque it makes.
It's been 1.36 60 ft. with an 11" converter.
'63 Dodge 330
11.19 @ 121 mph
Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs.
10.01 @ 133mph with a 250 shot of nitrous an a splash of race gas. 1.36 60 ft. 3,700 lbs.
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Re: 3.55 vs 3.91 track time differences?
[Re: GY3]
#3147899
05/31/23 08:39 PM
05/31/23 08:39 PM
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Joined: Aug 2003
Posts: 43,308
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,308
Bend,OR USA
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[quote=GY3]Nothing with that combo. We run a 3.54 gear with a 505" stroker and rear ratio seems to matter very little with the torque it makes.:  I ran 4 different rear gear ratios in my old pump gas stroker motor in my Duster, 3:73, 3,91, 4.10 and 4.30 with no other changes, other than running at different tracks. It ran within.08 and 1.0 MPH as long as it didn't spin   I did have a Mopar brand low gear drive set (2.77 I think) in the 727, best 60 ft was 1.42 I think 
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 3.55 vs 3.91 track time differences?
[Re: Jeff_383]
#3147917
05/31/23 10:56 PM
05/31/23 10:56 PM
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Joined: May 2003
Posts: 3,124
N.W. Florida
Fat_Mike
master
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master
Joined: May 2003
Posts: 3,124
N.W. Florida
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Well, I may look out for a 3.55 third member then. It does drive well with the 3.91's. Just want a little more on the freeway for some longer trips. I also really like the new PTC 9.5. If that's[/i] the goal (or the consideration), there are calculators that will tell you how much your RPM's will be affected. I think [i]the track will be the only way to truly figure out the affect at the track.
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Re: 3.55 vs 3.91 track time differences?
[Re: Jeff_383]
#3147919
05/31/23 11:38 PM
05/31/23 11:38 PM
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Joined: Jan 2003
Posts: 31,078
Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,078
Oregon
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Well, I may look out for a 3.55 third member then. It does drive well with the 3.91's. Just want a little more on the freeway for some longer trips. I also really like the new PTC 9.5. If you want a higher gear for the freeway then go with the 3.55 gears. Sounds like the car is more of a driver than an all out drag car so make it work for what you want it to do. It isn't going to slow down much at the track. In fact, if it is traction limited then it might actually leave the line better with the taller gear.
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Re: 3.55 vs 3.91 track time differences?
[Re: Jeff_383]
#3147966
06/01/23 11:17 AM
06/01/23 11:17 AM
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Joined: Dec 2013
Posts: 4,704
Wichita
GY3
master
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master
Joined: Dec 2013
Posts: 4,704
Wichita
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Well, I may look out for a 3.55 third member then. It does drive well with the 3.91's. Just want a little more on the freeway for some longer trips. I also really like the new PTC 9.5. You say "third member". If you're planning on hooking this combo at the track with slicks, you're going to need to upgrade to something stouter than an 8 3/4.
'63 Dodge 330
11.19 @ 121 mph
Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs.
10.01 @ 133mph with a 250 shot of nitrous an a splash of race gas. 1.36 60 ft. 3,700 lbs.
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Re: 3.55 vs 3.91 track time differences?
[Re: GY3]
#3148019
06/01/23 04:06 PM
06/01/23 04:06 PM
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Joined: Feb 2003
Posts: 4,953
Houston, Texas
TheOtherDodge
master
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master
Joined: Feb 2003
Posts: 4,953
Houston, Texas
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Nothing with that combo.
We run a 3.54 gear with a 505" stroker and rear ratio seems to matter very little with the torque it makes.
It's been 1.36 60 ft. with an 11" converter. That is a little deceiving. Unless you are saying you went 1.36 N/A. On my 389 small block, I run a 3.55 gear and have gone 1.37 60ft.... but... there is more to that statement...
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Re: 3.55 vs 3.91 track time differences?
[Re: TheOtherDodge]
#3148022
06/01/23 04:24 PM
06/01/23 04:24 PM
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Joined: Dec 2013
Posts: 4,704
Wichita
GY3
master
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master
Joined: Dec 2013
Posts: 4,704
Wichita
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Nothing with that combo.
We run a 3.54 gear with a 505" stroker and rear ratio seems to matter very little with the torque it makes.
It's been 1.36 60 ft. with an 11" converter. That is a little deceiving. Unless you are saying you went 1.36 N/A. On my 389 small block, I run a 3.55 gear and have gone 1.37 60ft.... but... there is more to that statement... 1.54 60 ft. N/A There, how's that? 
'63 Dodge 330
11.19 @ 121 mph
Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs.
10.01 @ 133mph with a 250 shot of nitrous an a splash of race gas. 1.36 60 ft. 3,700 lbs.
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Re: 3.55 vs 3.91 track time differences?
[Re: GY3]
#3148139
06/02/23 09:55 AM
06/02/23 09:55 AM
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Joined: Feb 2003
Posts: 4,953
Houston, Texas
TheOtherDodge
master
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master
Joined: Feb 2003
Posts: 4,953
Houston, Texas
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Nothing with that combo.
We run a 3.54 gear with a 505" stroker and rear ratio seems to matter very little with the torque it makes.
It's been 1.36 60 ft. with an 11" converter. That is a little deceiving. Unless you are saying you went 1.36 N/A. On my 389 small block, I run a 3.55 gear and have gone 1.37 60ft.... but... there is more to that statement... 1.54 60 ft. N/A There, how's that? LOL, much more applicable! 
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Re: 3.55 vs 3.91 track time differences?
[Re: FurryStump]
#3148365
06/03/23 10:17 AM
06/03/23 10:17 AM
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Joined: Jan 2003
Posts: 2,937
A shed in England
Tig
master
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master
Joined: Jan 2003
Posts: 2,937
A shed in England
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Flash rpm yes, stall no. Rear gear has no effect on stall and it really only changes flash rpm because of how flash rpm is defined, not a “real” change to the actual flash rpm. The change is the car just moves easier/sooner. So yes the rpm will be lower when the car first moves, but you can still get to the power band quicker during the run. (The reason we play with flash in the first place)I went with a low gear set 904 which would “lower” my flash rpm, but because the car is moving, I would get to peak torque .5 second quicker in the run, even with the “reduced” flash rpm.
Just for info, rear gear changes did have an effect on stall speed on my combo, verified by the racepak.
'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials.
9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge.
RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03
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