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#1
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Help! 3.91's or 3.55's
I need some opinions. I am currently running 3.91's on a small block. I am currently building a 440 for the car and I am debating changing to 3.55's. The car will see much more highway than strip and it will be a mild buildup (400-450 horse) The highways in FL are 70 mph, and the 3.91's rev pretty high. Would the 3.55's complement the big block better than the 3.91's for general cruising? I am looking for better drivability, but I am not sure that 3.55's will lower the revs that much.
Thanks for the comments. |
#2
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I run 3.55's behind my pretty mild 440 (low 13 sec car) if you plan on doing A LOT of highway cruising, even the 3.55's will rev too much. I am talking about a lot of cruising, like going more than 20 or 30 miles at a clip on a regular basis. I figure I am turning about 3500 at 70 mph. the torque of the 440 should get you moving pretty good whichever gears you have in it. for local cruising and once in a while blasts down the interstate, either 3.55's or 3.91's are tolerable.
I will probably get flamed by all the guys with 4.56's in thier daily drivers that go 100 miles each way to work at 90 mph, but this just my opinion. at 3 or 4 grand, even the coolest sounding motor can get old after a while. |
#3
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I had a 3.23 gear in a 4000lbs B body with a mild 440 with app. 425-450h.p. and the best et. was 13.32 and r.p.m. @70 mph was 3000. Then I switched to a 3.91 gear to see what it would do and it went a best of 13.07 and @ 3000rpm would only be doing 60mph. Gas milage also went down big time with the 3.91s. Not really worth the few tenths in the 1/4 in my mind. I,m going back to the 3.23s and possibly a G.V. overdrive since this is mostly a cruising car. Just my .02 cents but even 3.23s with 26" tires are just to many revs if your gonna be doing alot of highway driving.
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#4
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remember that tire size plays a big role also when selecting a gear.i run 3.91 's in my 440 car and run a 28 " tire.i tach @3500rpm at @65mph.when i was running a 26 " tire i was at 4000+ rpm at the same speed.changing the tires made the gears much more tolerable on the highway.
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#5
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Yep
I run 3.91's with a 440, the 3.55's was much better on everything. The 3.91's help me at the strip, but killing the engine in the process. I thought about diggin out the 3.23's for a while and do some reall cruising. There the best cuising gears. I would think 3.55's and 3.91's (with at least a 27 inch tall tire) gets the best of both worlds.
__________________
68 Coronet 69 Super Bee......new 500 cid comin soon! 73 Duster witha missing 440/727 |
#6
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3.55 with a GV OD, A-518 upgrade, or a Keisler 5-speed conversion would be a great way to go.
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#7
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I have been driving the '69 R/T Convertible with the 4.10:1 Dana (that's how I bought the car) and I'm ready to switch to the original 3.54:1 gears after just driving it about a hundred miles.
With the 4.10 gears I can easely take off in second gear and shift to 4th at 10 MPH without lugging the engine. With an automatic trans, if you have a 3,000 RPM stall converter the 3.55:1 gears are about as high a ratio you would want or the converter will be below the stall speed most of the time. If you have a tighter converter you can use higher hears like the 3.23:1 gears. |
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