8 1/4 vs. 8 3/4

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j par

j par

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I'm having trouble finding threads? I'm sure there's plenty. I have a 8 1/4 rearend 355's with a track lock.
I'm only in it $400. With the new stroker coming with 4 speed. I'm thinking this might be the first to go/blow?
 
I think you'd be correct. If you're serious on radials, just go fab'd 9", and skip all the wasted money and blown up stuff.

For street use, I'd just drive what you have and try not to hoon too much while I saved for the 9". S/F....Ken M
 
If you are looking for information as far as comparing the two , there is no comparison...........hence no threads. :D
With a stroker and a four speed , the 8 3/4 might be considered a marginal piece.
Without a diet and some wheel spin , it will be something to keep in mind.
If the car wants to really hook , I'd explore other options.
 
j par said:
The 73 duster is on a diet, but I'm not necessarily nice to it !
Click to expand...

Have you had a chance to weigh your 73 duster yet? I ask is because i am also building a 73 duster and would like to see what yours weighs at. If you are going to race it with some slicks i would skip the 8-1/4 and go to a 8-3/4. here is what i did to my Richmond 4.10 geared 8-3/4 on my 5th pass at the track. this was with a 3520 pound big block dart and M/T 275/60/15 ET street radial. after i got home i installed a used set of 4.30 gears left over from my 65 Plymouth. so far the rear is holding up but i know i am on borrowed time. I have a Dana i am going to install some day when i get the money. well the good thing is if you do brake your 8-1/4 at least you wont have to pull the trans to check the sprag like i did.lol also i would like to see some pics of your duster. thanks mopar65
 

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j par said:
The 73 duster is on a diet, but I'm not necessarily nice to it !
Click to expand...


How big of a tire for traction? :burnout:
Type of wheel?

I bought some 10" wide (Steel) Rallyes to go on a project.
Man, Are they heavy.

will save them for a street cruiser,
bought some Weld wheels,
they weigh less then the Rallye wheel

Rallye wheel only vs Tire and weld wheel
 
Over the winter got some 10" weld 15's for the 26-10-15's cheater slicks for dragstrip. Last summer i got a great deal on some 05 magnum wheels- 18's. I'm not a big fan of big rims, but $200 for rims and 90% tires? 18's it is ! (For now) I'll trade if someone likes that look?
 
I've got about 20 passes with the 318, but I'm sure the stroker should have another 100 horsepower. When the track lock was put in everything looked good.
 
j par said:
I've got about 20 passes with the 318, but I'm sure the stroker should have another 100 horsepower. When the track lock was put in everything looked good.
Click to expand...

How many Cubic inches and compression
That 4 speed is still gonna beat the rear end up.

I would be watching for a Dana to build

The tubes are .500" thick

 
Both my cars have had the D-60 rear.... If I were starting from scratch like the OP, it would be aftermarket 9" style all the way.

that said, if you are persuaded to the D-60 route, there is no better phone call to make...http://www.doctordiff.com/
 
The 8-1/4 is medium strong.
The 8-3/4 is pretty strong.
The DANA is best.

In the street, the 8-1/4 would be fine for a cruiser with a few street burnouts.
On a street strip application, the 8-3/4 would be OK on a limited track use. 1 or 2 times a year at the track.
The DANA will take it all down no problem.
If this is mostly track use, I think I would have to go with the guys and vote DANA.

Do you have any idea what kind of power the engine is making?
A brief description of the parts used?
Cam size, state of heads, intake & carb.

The thing about 4spd cars is the amount of shock the drivetrain receives on launches.
I tend to walk mine out and lay into the throttle as much as possible before wheel spin. Also, changing gears, I also try and limit the throttle as not to do anything more than chirp the tires and then, Again, lay into the throttle as much as possible but not loose traction.

While this method doesn't allow for the quickest runs , ET, it doesn't hammer the rear.
The car is a full steel '73 Cuda (3650lbs.) w/4.10'a on street tires but not a stroker. 360 CID, 11-1, solid cam @ 248 @ .050 Edelbrock heads. Very limited track use, lots of street abuse.
 
rumblefish360 said:
The 8-1/4 is medium strong.
The 8-3/4 is pretty strong.
The DANA is best.

In the street, the 8-1/4 would be fine for a cruiser with a few street burnouts.
On a street strip application, the 8-3/4 would be OK on a limited track use. 1 or 2 times a year at the track.
The DANA will take it all down no problem.
If this is mostly track use, I think I would have to go with the guys and vote DANA.

Do you have any idea what kind of power the engine is making?
A brief description of the parts used?
Cam size, state of heads, intake & carb.

The thing about 4spd cars is the amount of shock the drivetrain receives on launches.
I tend to walk mine out and lay into the throttle as much as possible before wheel spin. Also, changing gears, I also try and limit the throttle as not to do anything more than chirp the tires and then, Again, lay into the throttle as much as possible but not loose traction.

While this method doesn't allow for the quickest runs , ET, it doesn't hammer the rear.
The car is a full steel '73 Cuda (3650lbs.) w/4.10'a on street tires but not a stroker. 360 CID, 11-1, solid cam @ 248 @ .050 Edelbrock heads. Very limited track use, lots of street abuse.
Click to expand...
Sorry if this sounds familiar - it's a copy/paste from my "question of the day?" Thread a couple of weeks ago.e day! ??

horsepower could be the question of the day? !
×2 600 cfm edelbrocks tunnel ram, 596heads (home porting- smoothing exhaust ports/ opening under all seats just a little bit- not getting carried away here I'm a first timer) then back to the shop for valve job-1.60/1.88 . Solid cam (regrind) cam- duration@ .50 - 259/267 lift gross 546/566 lash .026/.028 lob sep. 104/110
Av. 107. 273 rockers. 360 block, scat stroker (cast) crank, scat I-beams, icon forged flat tops - 10.8 : 1 with 70cc heads.*

Of course this will be in my 73*duster
gutted
4 speed
355 sure grip
26 in street slicks

Hopefully the 8 1/4 rearend will last long enough to see if 355's are the best? I've heard of the 8 1/4
rearend lasting a long time with less than 500 horsepower ? The heads, valves, and cam is pretty small?
 
The 3.55's are limiting. I myself would be looking 4.30 gears.
It does look like your about to have some fun though! (A little envy here)

Thanks Leblanc
 
Looking at one of those rpm calculators - 4th gear = 1:1 (355's) with 26in. Tire, 115pmh @ about 5200rpm's. Now I'm totally guessing 5200rpm's is going to be this motors sweet spot ???? IF and thats a big ( IF ) I can pull off 115mph - I'm hoping to pull off a low 12 and dare i dream ? High 11's ! !??
 
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