3.91s in my 340 now!

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Rude72*

Rude72*

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Hey guys...

I have a '72 340 Duster with a few engine mods (Holley 750, bored .030 over, Mopar performance purple cam/P4120235, Hooker comp headers, Edlebrock Torker II intake, 2.5" exhausts with Flowmaster mufflers). It has a Mopar 727-A three speed auto trans with a 3200 RPM Stahl Speed Trans Specialties converter and B&M shift kit with Hurst Quarterstick. It originally had 3.23s in it when I bought it, but it seemed (to me at least) that it was kinda "doggin" it coming out of the hole. Well, that certainly has changed! I was wondering if anyone else out there is running 3.91s with their 340s and how you're liking/disliking it.
 
I also have a 72 340 Duster that originally had 3.23s and have swapped to 3.91s. Although my 340 is now 422” and I run a 4 speed. In my opinion 3.91 and a 4 speed are a match made in heaven for a street car.
 
SSG_Karg said:
I also have a 72 340 Duster that originally had 3.23s and have swapped to 3.91s. Although my 340 is now 422” and I run a 4 speed. In my opinion 3.91 and a 4 speed are a match made in heaven for a street car.
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Man, do I wish I had a 4 speed tranny! 3,500 RPM around 60 mph is a little steep, but I would never go back to the 3.23s. It's not a daily driver and I won't be driving all over the place for car shows... a couple times a year I might be making an hour to an hour and a half drive. Thanks for sharing!
 
I put 3.91s in Vixen for a short time. I really enjoyed it behind the hot slant 6, but with 13" tires it was buzzin goin down the road, so I put the 3.23s back in.
 
RustyRatRod said:
I put 3.91s in Vixen for a short time. I really enjoyed it behind the hot slant 6, but with 13" tires it was buzzin goin down the road, so I put the 3.23s back in.
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thats probably. what Ill do. 3.91 in my 70 Dart. I also have a 741 case 3.23 and a 2.94.
3.91s for a while, 2.94s long cross country trip
3.23s rathole spare stash
 
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