Gear change/ 60' loss
#1326969
10/27/12 03:11 PM
10/27/12 03:11 PM
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Joined: Feb 2009
Posts: 1,532 off the grid
340B5
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I need a gear change in my Duster and just 3 days ago had a new best of 1.49 60' and a 10.95 ET. Problem is that it hits the rev limit (7k) in 3rd around 1000'
I wonder how much 60' I will give up going from 4.86 to 4.56 gears? This is a 3.58 stroke 374 inch engine. Any guesses or personal experiences?
Yeah, it's got a smallblock.
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Re: Gear change/ 60' loss
[Re: 340B5]
#1326971
10/27/12 03:21 PM
10/27/12 03:21 PM
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Joined: Jan 2003
Posts: 1,142 Central New York
slippery440
Crybaby440
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Crybaby440
Joined: Jan 2003
Posts: 1,142
Central New York
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What size tire? Try a 2 inch taller tire and that would be close to the 4.56s.
If the MODS did their job I would not be hitting the notify MOD button. LOL
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Re: Gear change/ 60' loss
[Re: 340B5]
#1326972
10/27/12 03:24 PM
10/27/12 03:24 PM
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Joined: May 2003
Posts: 13,200 aZLiViN
J_BODY
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I Live Here
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Re: Gear change/ 60' loss
[Re: 70dusterjohn]
#1326973
10/27/12 03:35 PM
10/27/12 03:35 PM
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Joined: Feb 2009
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340B5
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Quote:
We lost none, at all... I really dont think that the 56 is going to be a big enough drop to make a difference, I think I gained maybe 200 or so rpm. So I still feel that you would hit the rev before the line. I ended up going to a 4.30 and the car picked up a little more on top end, and again lost nothing in the 60ft. Thats with a 30" tall tire..
I would be happy if I didn't loose any, and yes I thought about still hitting the limiter, but it should be for less time anyway.
Slippery: I already have the gears, so that fits the budget better.
J body: The combo should be done before that. I have factory iron J heads(worked over some)I'm gonna guess 6700 or so, but I haven't felt it nose over before the limiter. I've only made 5 complete passes w/ the combo and I'm still getting re-acquainted with the car after a 2 yr hiatus.
Yeah, it's got a smallblock.
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Re: Gear change/ 60' loss
[Re: Dodgem]
#1326975
10/27/12 04:54 PM
10/27/12 04:54 PM
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Joined: Jan 2003
Posts: 6,266 Renton Washington
Triple Threat
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master
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Posts: 6,266
Renton Washington
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If the converter is big enough, it shouldn't hurt too much, maybe .02 to 60 foot, but the car will run better down track...
-Dustin 67 Dart, 9 second, 392" G3 Hemi 68 Barracuda 340 F/SA
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Re: Gear change/ 60' loss
[Re: 70dusterjohn]
#1326978
10/27/12 05:16 PM
10/27/12 05:16 PM
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Joined: Feb 2009
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340B5
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Thanks for the replies. It looks like I'll be good to go w/ the 4.56's. The trans has the 2.74 low anyway.
Yeah, it's got a smallblock.
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Re: Gear change/ 60' loss
[Re: 340B5]
#1326979
10/27/12 08:22 PM
10/27/12 08:22 PM
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Joined: Jan 2003
Posts: 10,011 Frostbitefalls MN (Rocky&Bullw...
gregsdart
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going from 4.86 to 4.56 is only a 6.2 percent drop in gear ratio, so it should see 400 rpm drop. I am betting it will run as good or better. With the 2.74 low you still have a 12.49 starting line ratio, and that is pretty high.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Gear change/ 60' loss
[Re: tboomer]
#1326981
10/27/12 09:23 PM
10/27/12 09:23 PM
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Joined: Jan 2004
Posts: 903 Saskatchewan, Canada
cudabin
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Saskatchewan, Canada
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One school of thought is that you should peak at the 1,000 foot mark which by then most of the acceleration has reduced your ET and you are already at a higher MPH for the last 320 feet...
This assumes the engine can handle the rpm and is not nosing over...
My motor made peak HP at 7,200 rpm and I cross the stripe at 8,000 - 8,100 rpm. I think it ET's decent...
Best way to find out is to test it, so let us know how the 4.56's affected the ET and MPH once you cahnge.
Cheers,
Arnie
67 Cuda 8.48@ 158.7 mph 1.18 60' 2,600 DA(so far...)
70 Super Bee 440 Six Pack 4-speed. 13.2 @ 104 Stock exhaust/Street tires.
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Re: Gear change/ 60' loss
[Re: perfmachst]
#1326983
10/28/12 11:24 AM
10/28/12 11:24 AM
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Joined: Feb 2009
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340B5
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I've tried to factor in everything. The tires will turn 7.6 times in 60', stall is increased ever so slightly w/ the 4.56's, etc. I think I'll check the logbook today and see what going from 4.56 to 4.86 did for the 345 in engine a few years back.
Yeah, it's got a smallblock.
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