Different Gear?

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DusterDaddy

DusterDaddy

sledgehammer mechanic
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My 74 Duster has freshened 74 cast date stock bore 318. I bought the engine carb to pan after it was boiled and built by a third party I can not locate.
Here is what I know about the motor. The bottom is stock. The cam is a Mopar performance piece that produces .480 lift. The heads are 1974 cast date 318 heads with a fresh 3 angle 1.88/1.60 valve job with nice porting and blending work. Intake is Edelbrock Performer gasket matched ported to heads. Exhaust manifolds are 1970 340 high performance pieces also gasket port matched. Carb is Edelbrock 1406. Ignition is recurved stock electronic ignition distributor with Petronix Flamethrower HEI. Exhaust is 2.5" straight old school dual with Thrush welded mufflers. Torque converter is the stock "high stall" unit used in the 1970 Duster. A true budget set up, but I gotta say the car goes like hell!
The rear is an open diff 8.25. I want to get a suregrip unit and some gears that will perform better than the highway gears I have now, although I like how the car drives on the highway!
What would you do?
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What ratio do you have now? I would use 3.55 or 3.23's for a driver, maybe 3.91's if you don't plan any long trips. If you plan on returning the A/C I would go w/ nothing deeper than 3.23's.
 
Demonic said:
What ratio do you have now? I would use 3.55 or 3.23's for a driver, maybe 3.91's if you don't plan any long trips. If you plan on returning the A/C I would go w/ nothing deeper than 3.23's.
Click to expand...

My buddy has a DartGTS with a 340 and he has tried a bunch or ratios and loves the 355.
My plan is to bring back the AC one day...
 
I don’t know what size gear is in there now. I’ve never had the cover off of the rear end.
 
OK, then I myself would run 3.55’s.
A better converter would help a lot.
 
Me? Suggestion for what? A torque converter?
Call Lenny @ Dynamic
Exhaust, install an H or X pipe
Looose the exhaust manifolds for Doug’s or TTI headers
Ditto with the Performer and use a rpm-ag or Weiand stealth.
Use the AVS model carb instead of the AFB or go FI w/a Holley Sniper
Whew! I’m beat spending internet money....
 
lol
You can keep the rest. But I’ll take the 355 gears for this years improvement
 
A modern transmission is another option. It may have a lower 1st gear and an overdrive final drive. This allows you to run a 3.00 rear end but still have good pickup because of the lower 1st gear, and still have low RPM on the freeway because of the 3.00 and the overdrive.
 
Eight and a quarter is plenty strong enough for the gears you want and the Sure Grip you want and leave the rear end in there.
 
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I got lucky and had a friend who got a eight and a quarter with 3: 55 gears open out of a Dakota truck. He welded the perches on the bottom side. I paid 100. Then I found a guy on eBay who is selling a Sure Grip for $100 and another Stroke of Luck he lived here in town and installed it for another hundred dollars. My Stroker with four Speed and slicks did not take this rear end out, but when I built an 8 and 3/4 it only took 20 passes and kaboom.
Now- D60 and done...
 
My 74 duster had a 2.45 gear open 8.25, it was a stock 318 2 barrel so you'd have to change the carrier to use a better gear.
 
Find your ratio before proceeding further. If it’s one of ratios higher than 2.76:1 (I.e. 2.45, etc.) you’ll have to have a different housing to swap gears out. Read the article about 8-1/4s here on FABO.
 
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