Re: 3.23 vs 3.91
[Re: FM370RR]
#297222
04/23/09 11:06 AM
04/23/09 11:06 AM
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Joined: Dec 2007
Posts: 7,759
So Cal
HealthServices
Why would you even post that?
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Why would you even post that?
Joined: Dec 2007
Posts: 7,759
So Cal
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Not worth it for me I went down for now. 3.91 to 3.55 but I have a shorter tire.
Allen
Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first.
Life was a little easier when I was just a wrench.
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Re: 3.23 vs 3.91
[Re: HealthServices]
#297223
04/23/09 11:25 AM
04/23/09 11:25 AM
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Joined: Apr 2007
Posts: 2,327
Glendale, AZ
69L78Nova
Banned. Forever.
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Banned. Forever.
Joined: Apr 2007
Posts: 2,327
Glendale, AZ
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Depends on your setup and what youre running
1969 Nova
454/M21/3.31
Mild mid-11 second weekend cruiser
1994 F150 XLT Super Cab 2WD
5.0/4R70W/3.55
(Daily driver)
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Re: 3.23 vs 3.91
[Re: burdar]
#297224
04/23/09 12:24 PM
04/23/09 12:24 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
I ran a best of a 13.55 @ 89mph with 3.23's and 235-60 tires. I installed 4.10's and 29X10.5" slicks and ran a best of 12.71 @ 106mph.
I think that is a little better than average. I have heard that you will only gain up to a half second with a gear change.
something doesn't add up....what else did you change on the car? there's no way you picked up 17 MPH with just a gear change. your MPH should be pretty close to the same independent of gear ratio.
assuming 29" tall tire, and no converter slip RPM at 70 MPH will be 2620 for 3.23's and 3175 for 3.91's I'd assume 5-7% slip, which would raise the RPMS to 2750-2800 RPM's for the 3.23's and 3334-3400 RPM for the 3.91's.
Last edited by patrick; 04/23/09 12:30 PM.
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: 3.23 vs 3.91
[Re: Mr.Yuck]
#297226
04/23/09 12:47 PM
04/23/09 12:47 PM
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Joined: Oct 2006
Posts: 7,367
Iowa
burdar
Owen's Dad
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Owen's Dad
Joined: Oct 2006
Posts: 7,367
Iowa
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Quote:
something doesn't add up....what else did you change on the car? there's no way you picked up 17 MPH with just a gear change. your MPH should be pretty close to the same independent of gear ratio.
I don't know what to tell you. That's what it ran. It was a stripped down 82 Cordoba that still weighed over 3400 lbs. I had a 360/904 with a 3500 stall convertor in it. 235-60 BF Goodrich drag radials and 3.23's. The best I could do was a 13.55 at 89mph. During the winter I put in 4.10's and a spool and ran Hoosier 29X10.5 slicks. I might have also put a Holley electric fuel pump on it that winter too but that was it.
My first pass on the slicks I left easy and then hit it after 60 ft and it went 13.06 @ 102mph. The next pass it jumped out of gear at the end of the track. After I adjusted the shifter cable it went 12.91 @ 103mph.
At the track I usually ran at I got it to go the 12.71 @ 105.8mph early in the morning. It usually ran between 102 and 103 mph during the rest of the day.
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Re: 3.23 vs 3.91
[Re: burdar]
#297227
04/23/09 01:32 PM
04/23/09 01:32 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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the fuel pump could explain it. sounds like the old fuel pump wasn't keeping up and feeding the beast at high RPM, and the engine was laying down some on the big end of the track, keeping your ET & MPH down. playing with an online calculator, http://www.dragsource.com/index.php?navselect=calculators&calctoview=4assuming 3600 lb with driver, an 89mph trap and a 15.31 ET yield the same HP estimation. a 106 trap and a 12.83 yield the same HP estimation.
Last edited by patrick; 04/23/09 01:33 PM.
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: 3.23 vs 3.91
[Re: Mr.Yuck]
#297228
04/23/09 01:45 PM
04/23/09 01:45 PM
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Joined: Jan 2003
Posts: 1,092
BRawls
super gas
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super gas
Joined: Jan 2003
Posts: 1,092
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Quote:
depends...w/ slicks and the correct stall a ton. I went from 14.11's in a 383 charger to 13.48
Slicks will make a bigger difference than the gear change in my experince.
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Re: 3.23 vs 3.91
[Re: patrick]
#297230
04/23/09 05:44 PM
04/23/09 05:44 PM
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Joined: Feb 2005
Posts: 4,313
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,313
Prospect, PA
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Quote:
the fuel pump could explain it. sounds like the old fuel pump wasn't keeping up and feeding the beast at high RPM, and the engine was laying down some on the big end of the track, keeping your ET & MPH down. playing with an online calculator,
http://www.dragsource.com/index.php?navselect=calculators&calctoview=4
assuming 3600 lb with driver, an 89mph trap and a 15.31 ET yield the same HP estimation. a 106 trap and a 12.83 yield the same HP estimation.
This is it exactly - the fuel pump. A gear change might add 1 mph. Look at the old 60 ft, and compare it to the new 60 ft, multiply that difference by 1.5, and that is about the net benefit of just the gear/tire change.
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