3.91 gears???

[1971scamp383]

hi here is my build...1968  383 .030 over...stock crank polish and new bearing... edelbrock 7194 camshaft: Duration at 0.006" Lift: Intake: 300° Exhaust: 308°
Duration at 0.050" Lift: Intake: 238° Exhaust: 246°
Lift at Cam: Intake: 0.320" Exhaust: 0.330"
Lift at Valve: Intake: 0.480" Exhaust: 0.495"...with matching valves springs....edelbrock double roller timming chain...edelbrock torquer aluminium intake.....edelbrock 750 cfm performer series....full length hedman headers 1 7/8 ..3'' out....440source aluminium heads(2.14 1.81 valves 84cc) ....keith black dome pistons..(6cc dome)...10.1cr.....2500 torque stall(stall at 2900 rpm)..... lakewood traction bars... i want it to be a street car and some road...about 50-55 mph on road...speed limit is 55 mph aroud here.... and to have some fun at the track(ran 10.70 1/8 miles with old and tired 2bbl 383 and 2.76 open)... !!!(1968 monaco 500 convertible...4100lbs) i was wondering what you guys is thinking about that....3.55 or 3.91???(27 inch rear tire)....a friend told me than im gonna blow the engine with 3.91....but i want some pull!!! thanks

[Blvedere]

IMO... If you are going to run the 1/8 with 3.91's then it should be ok. But if you are looking at the 1/4 that small tire will let the engine rev to high.

[1971scamp383]

only 1/8 miles !!!!!no 1/4 aroud here

[IL.DART340- 4SP]

 In my opinion for what you are doing with your build I would do the 3.91 Plus according to your post no 1/4 runs only 1/8th mile. Not a big fan of traction bars on a Mopar. So you wanted opinions thats my 2 cents worth.

[ksdartguy]

3.91 will work fine.
I had 4.10s with close setup to yours.
Rick

[edorion]

I've got 3.91s and 27" tires on my 68 Barracuda no problems. It is buzzy on the freeway-65-70 mph, but you won't "blow your engine".

[nightrider]

I have those in mine... you won't blow your engine, I had them with a 26" tire on back and ran 3300 RPM at 120km/h... with a 27" tire you should be good at around 3100 RPMs... This is ideal because on the freeway you do not want to have your cruise RPMs be below your stall speed or that can damage the transmission... other than that, give'er hell! haha

[guzzimike]

I've got 3.91s and 27" tires on my 68 Barracuda no problems. It is buzzy on the freeway-65-70 mph, but you won't "blow your engine".

 

[DustBuster]

If 90% of your driving is on the street, I'd consider 3.55's (maybe someone makes a 3.70 gearset which would be a perfect compromise)

[maxwedgedart]

391s are fine just use 29.5 to 31 tire rpms will be fine 27, 28 to small. i had 29.5 hoosiers shifted 6200 went through traps 6000rpms know i have 31 hossier and go through traps 6300rpms 1/4 mile runs i run 10.39@128 147 60ft 3470lb dart 68 all street trim glass hood only 440 60 over 452 cast heads stock crank flat top pistons, solid roller cam indy intake single dominator the car is in the oct/nov issue of MOPAR ENTHUSIAST MAG. PAGES 44-49 CHECK IT OUT!  need help just ask.

[383man]

My son uses 3.91's in his Dart with 26 x 9.5 Hoosier QTP tires.  He cruises about 3000 at 55 to 60 mph.  At the track they work good with his 400 and he might even go faster with more gear.  Last time out he was shifting at 6700 and trapping about 6400 and he ran his best yet of 11.40's.   But he drives it alot so the 3.91's will stay in it.  Ron

[ksdartguy]

They make a 3.73 in Yukon gears. Personally though 3.91 isnt too steep.
Especially if you race 1/8 mile too.
Rick

[mopar_eric]

I have 3.91s on the dart. Good for around town and great at the strip also (27" tire)

No good for 100 mile trips though... but if you're road tripping you can have a highway pumpkin with open gears for that on the shelf.

Eric

[edorion]

I took my Barracuda on a 100 mile trip with 3:91s. I wouldn't do it on a regular basis, but other than driving in the slow lane @ 65-70 I had no problems and managed to get 17 mpg, it usually averages 10.3mpg 

[73swinger]

I run 3.91s in mine. I like them but am glad to be going to a taller tire this winter. I was running about a 25" tire and it revved 3000ish at about 80km/h. At the end of a quarter its almost bouncing off the rev limiter at 6200. I'm switching to a 28" TIRE

[383man]

Well I use the 9.5 Dynamic street/strip convertor that will flash about 4200 at the track.  Now I have 4.30's with a 29.5" tire on my 63 and I drove it 120 miles last summer cruising about 60 mph at 3200 rpm all the way.  No slipping at all as it drives around like a normal convertor.  In fact I drive it all the time between 30 and 60 mph and it always drives great.  And at the track it flashes and launches great when I foot brake it to about 2200 and then mash it on the last yellow.       Ron

[73swinger]

I believe that a high stall converter that's "built correctly" will only stall at full throttle (flash stall) or when you are braking and gassing at the same time. a good one should behave somewhat normally if you are driving normally. Shitty one's will slip all the time causing high heat buildup