Headers & Cam upgrade or Rear Gears

[Dustine]

Hi,

New to the site looking for some advice on performance upgrades on my 72 Duster 340 . The car is all stock 70K original mile survivor 340 904 8 3/4 3:23 SG 225/70/14 tires stock converter Edelbrock 600 carb stock CI intake stock exhaust manifolds . On the fence if I should do a cam swap and headers or just upgrade the rear gears to 3:73’s or 3:91’s ? The car will be 100 % street car and very little highway use . Just looking for more seat of the pants fun light to light . I’m not looking to change the converter from stock . I think the least expensive option would be a rear gear swap just wanted to know if I would feel that much of a difference from the 3:23’s

 

[TF360]

That's a nice combo you already have. You would feel a big difference with 3:91's, but you lose the relaxed highway cruising

 

[Oldmanmopar]

Converter would be the best bang for the buck. 340's came with 727 and a 3500 stall that stalls at 2800-3200 depending on engine torque. Owned many in the early 70's. . I also worked as an installer at Cottman Transmission. I would take all the mopar performance converters home. They would never reuse them on the gold lifetime units.

Find a 71 904 or 727 and install it with a 3500 converter. Keep the 323's . If the trans is set up right you should melt the tires from the start through second while in drive. Part throttle kick down servo 71 factory trans and a 340/ Hemi governor. will wake any car up. These mods can be done in the car except for the converter.

I can remember back in the 70's auto on column. left elbow out the window while shifter in drive. Look over at your competition and stab the throttle. Let er rip tater chip!

 

[318willrun]

Welcome to the site. If you ONLY care about stop light to stop light and it won't see the highway and you won't change the converter, then slap in a set of 4.88's

 

[rumblefish360]

Hi,

New to the site looking for some advice on performance upgrades on my 72 Duster 340 . The car is all stock 70K original mile survivor 340 904 8 3/4 3:23 SG 225/70/14 tires stock converter Edelbrock 600 carb stock CI intake stock exhaust manifolds . On the fence if I should do a cam swap and headers or just upgrade the rear gears to 3:73’s or 3:91’s ? The car will be 100 % street car and very little highway use . Just looking for more seat of the pants fun light to light . I’m not looking to change the converter from stock . I think the least expensive option would be a rear gear swap just wanted to know if I would feel that much of a difference from the 3:23’s

3.91’s. Then do wider tires. Something like 245/60/14 should be available. Tire diameter will change the speedometer reading. A new gear in the trans should help a lot.

 

[Dustine]

3.91’s. Then do wider tires. Something like 245/60/14 should be available. Tire diameter will change the speedometer reading. A new gear in the trans should help a lot.

How much of a difference do you think the 3:73’s would make ? And do you have any information on the new gear in the trans you mentioned ?Any idea what that would cost me at a reputable transmission shop ? Sorry for all the questions not to familiar with the internal parts of a transmission.

 

[rumblefish360]

How much of a change would it feel like?
A good bit for sure.
Where to get a new gear?
Here or Year One or the like place. Year one has a table on what gear ratio & tire size combo with what gear is needed.
What would a trans shop charge?
If there good fellas, nothing or maybe a cup of coffee.

The gear is easily changed by yourself with only 1 nut to be removed on the outside of the transmission where the speedometer cable goes in. Remove the bolt, the metal “Y” retainer under it, pull the cable and the whole assembly pops out. Take the gear (on a stick) swap, shove back in, replace retainer and bolt, tighten, your done. The only other thing is to “Clock” the housing to the Corresponding amount of teeth on the gear. It is marked on the outside underneath the white plate. Just clean the grease off and you’ll see the numbers.

 

[Dustine]

How much of a change would it feel like?
A good bit for sure.
Where to get a new gear?
Here or Year One or the like place. Year one has a table on what gear ratio & tire size combo with what gear is needed.
What would a trans shop charge?
If there good fellas, nothing or maybe a cup of coffee.

The gear is easily changed by yourself with only 1 nut to be removed on the outside of the transmission where the speedometer cable goes in. Remove the bolt, the metal “Y” retainer under it, pull the cable and the whole assembly pops out. Take the gear (on a stick) swap, shove back in, replace retainer and bolt, tighten, your done. The only other thing is to “Clock” the housing to the Corresponding amount of teeth on the gear. It is marked on the outside underneath the white plate. Just clean the grease off and you’ll see the numbers.

Thanks for all your help I think I will take your suggestions and see how it does with a gear change