BB Gearing ?
#813206
09/24/10 10:48 AM
09/24/10 10:48 AM
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Joined: Jan 2004
Posts: 910 Southern Oregon
toyotajeep
OP
super stock
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OP
super stock
Joined: Jan 2004
Posts: 910
Southern Oregon
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Hello, I am most likely going to be putting more miles on my "hot rod" than I had initially planned. That is a good thing for me I guess It is a 74 Dart Sport with a mild 440, SD intake, 750 or Theromquad on it, Headers, 3" exhaust. The cam is a MP .450-455. Car runs well. It has the factory HS convertor in it. Initially, I was building a mild engine, but I built the car for a better engine in the future. It does have 4.10's in it now. It will likely see a better set of heads and maybe a slightly bigger cam but that is about it. I need to drive a minimum of 40 miles each time I start it pretty much. Obviously 4.10's aren't going to cut it at 60-65 mph on a regular basis. At least for me they aren't. I have driven it a few miles with them and it was getting old already I am looking at a compromise gear. Something I can get mid-teens out of for MPG, and still run 13 something at the strip. Tire size is likely going to be 255/70/15 to match my rim size. If you were compromising, and wanted decent driveability with a relatively mild engine, and some performance, what ratio would you run? I'd rather err on the side of conservative. I am leaning towards 3.23's. Also, what am I likely giving up in the quarter dropping from a 4.10 to a 3.23? Thanks, ROB
1989 Dodge Cummins & 1989 Dodge W-250
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Re: BB Gearing ?
[Re: Mr.Yuck]
#813209
09/24/10 11:04 AM
09/24/10 11:04 AM
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Joined: Jan 2004
Posts: 910 Southern Oregon
toyotajeep
OP
super stock
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OP
super stock
Joined: Jan 2004
Posts: 910
Southern Oregon
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You know when I built it, I started with a slightly bigger cam in another engine. I never really drove it, but once I ran the numbers, I could see the same thing. Running out of RPM wouldn't be good in the quarter!
Years ago, with a 302 F..d Mustang I ran 2.79's and then 3.55's. It was night and day with a smaller engine. It did have some real short small rear tires though so it wasn't too great going down the road though. They were probably 3-4 inches shorter though.
1989 Dodge Cummins & 1989 Dodge W-250
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Re: BB Gearing ?
[Re: toyotajeep]
#813211
09/24/10 11:25 AM
09/24/10 11:25 AM
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Joined: May 2008
Posts: 5,399 Aurora, Colorado
451Mopar
master
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master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
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A 255x70x15 tire it really tall, about 29" so it will help reduce your RPM at speed. With 3.55:1 gears, 60 MPH would be about 2,500 RPM, and 70 MPH should be under 3,000 RPM (may vary a bit because of converter slippage and actual tire size.) going from 3.55 to 3.23 is a 9% change, so your rpms would be around 250-300 RPM less. Using a 255x60x15 tire (about 27" tall), and 3.55:1 gears, 70 MPH is about 3,150 RPM.
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Re: BB Gearing ?
[Re: 451Mopar]
#813212
09/24/10 11:34 AM
09/24/10 11:34 AM
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Joined: Jan 2004
Posts: 910 Southern Oregon
toyotajeep
OP
super stock
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OP
super stock
Joined: Jan 2004
Posts: 910
Southern Oregon
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I meant with the 4.10's and running out.
I agree, I don't think it would be close to an issue with the 3... gears.
I guess it comes down to 3.23's vs. 3.55's.
It may be helpful to know that with the exception of a trip or two a year, all of my driving will be done on 55 MPH posted roads. Everybody drives 63-67 but I wouldn't get run off the road at 60ish.
1989 Dodge Cummins & 1989 Dodge W-250
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Re: BB Gearing ?
[Re: toyotajeep]
#813213
09/24/10 11:44 AM
09/24/10 11:44 AM
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Joined: Nov 2007
Posts: 21,822 Kirkland, Washington
Pacnorthcuda
Too Many Posts
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Too Many Posts
Joined: Nov 2007
Posts: 21,822
Kirkland, Washington
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Quote:
I meant with the 4.10's and running out.
I agree, I don't think it would be close to an issue with the 3... gears.
I guess it comes down to 3.23's vs. 3.55's.
It may be helpful to know that with the exception of a trip or two a year, all of my driving will be done on 55 MPH posted roads. Everybody drives 63-67 but I wouldn't get run off the road at 60ish.
Based on that (a 60-65 crusing speed) and 29 inch tires, I would opt for the 3.55's
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Re: BB Gearing ?
[Re: toyotajeep]
#813214
09/24/10 12:13 PM
09/24/10 12:13 PM
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Joined: Jan 2003
Posts: 8,940 Holly/MI
Dean_Kuzluzski
master
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master
Joined: Jan 2003
Posts: 8,940
Holly/MI
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Given what your combo is, the amount of driving and the beastly mid-range of a warmly cam'd 440.........
I'd run the 3.55's with a very tall/fat rear tire. Dart Sport/Duster boddies will accomodate 275/60-15's and bigger to go with a 28" or taller.
Short tires look bad, as in not good, on the street and the 3.55's with a 26" slick would hook well at the track.
R.I.P.- Gary "Coop" Davis 02/09/68-05/13/04
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Re: BB Gearing ?
[Re: fourgearsavoy]
#813221
09/25/10 08:59 AM
09/25/10 08:59 AM
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Joined: Jan 2003
Posts: 21,072 Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,072
Niles , Ohio
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Foru Gear does yours run out of grunt on the top end.My 65 with 3.91s isnt pulling many revs in fourth.1 thru 3 is good as I shift at 6700.But once I hit 4th in the back end its loafing.Im thinking 4.30s or maybe even go back to the 4.88s.My tires are 28.5 tall.Rocky
Chrysler Firepower
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