Most low 12 second cars only run about 108-110 mph.
8 1/4 vs. 8 3/4
- Thread starter j par
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1970Duster
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Install a Rockwell rear and be done, you'll never have to worry about breaking one of those! If by chance you do happen to break a Rockwell, you might wanna rethink this hobby/interest, just sayin
j par
Well-hung Member
I've been doing a little internet research on the 8 1/4 and there's a lot of people out there swear by them that they will hold up? and there a direct replacement for the 8 3/4. I wonder if these people are just lucky?
Rocky_JS
'cuda
I would certainly check the 8-1/4 and make sure it is set right on.
j par
Well-hung Member
had a guy sell/install a trac lock this last summer over in Milwaukee. He used his little gages and painted the teeth and all that and said everything was fine.View attachment 20140513_123151.jpg
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i noticed you're close by? Do you go to any local car shows or to the track? I think there's a lot of a-bodys close by that don't do either. It would be great to get these people together once every couple months to swap knowledge & parts ? (Extra parts ) you know we all have them!
WA71swinger
Well-Known Member
I have a 727, not a manual trans in a 71' dart, complete interior, all stock body. mild 318. I've been racing street legal and mopar division for several years on an 8 1/4 with a dana cone sure grip carrier and 3:55 gear set. I've got hundreds of 1/4 mile passes/8-10, 000 street miles on the car with a very lead foot and lots of tire smoke. I even accidently threw the car in reverse one time with the pedal to the floor at about 30 miles an hour and spun the tires backwards enough to smoke show (oops. saw my dad and was going to "give him the pipes" LOL). So far the rear end has had no issues. The tranny on the other hand did not like it at all. I'm 3580# across a truck scale (several times) on the way to the track with a full tank of gas and a tool kit in the trunk. Got a fresh built 360, non stroker, about to drop in, should have approx. 100 more HP. Plan to race at least 15 weekends this year as well. We'll see what happens. Not sure if I would try it with a manual trans. Don't know if locker is more prone to break stuff. I roll off the line at around 1500 rpms at the track, then hammer it, because I know I am running an 8 1/4. Bracket racing don't care about your how fast your 60' is or your ET, just have to be consistent and have good reaction times.
I do have a dana with 410s setting on the side of the garage I need the disk brake set up for. There is a good chance I might need it this year. LOL
Other stock bodied/full interior car. 71 dart has 440 with an 8 3/4. 489 case, 3:91 gears. has many years of track time launching as hard as traction allows. Runs 12's with decent 60' times. Probably around a 100 passes last year. NO issues with rear except it chews up a lot of expensive street slicks. LOL
lots of guys running 3.91 to 4:56 and above gears, 11 and 12 second cars, with 8 3/4 rear ends at local track. running year after year. Only 1 that I know of is running a 4 speed. hopefully this is helpful to you in some way in your decision making processes.
I do have a dana with 410s setting on the side of the garage I need the disk brake set up for. There is a good chance I might need it this year. LOL
Other stock bodied/full interior car. 71 dart has 440 with an 8 3/4. 489 case, 3:91 gears. has many years of track time launching as hard as traction allows. Runs 12's with decent 60' times. Probably around a 100 passes last year. NO issues with rear except it chews up a lot of expensive street slicks. LOL
lots of guys running 3.91 to 4:56 and above gears, 11 and 12 second cars, with 8 3/4 rear ends at local track. running year after year. Only 1 that I know of is running a 4 speed. hopefully this is helpful to you in some way in your decision making processes.
WA71swinger
Well-Known Member
P.S. Good luck finding an a body 8 3/4. I've been trying for years so that I can just bolt it in and have it be all mopar. Rather than going to the dana. Anyone want to trade, let me know. You'll need the calipers, brake lines, etc.
j par
Well-hung Member
it is things like this that makes me feel I have a little time before I need to run out and buy a dana. But I'll be keeping an eye out for the right deal in the meantime. Again I'm hoping the 8 1/4 will last long enough to see if 355's are the best gearing?
8 1/4 is tough, 8 3/4 is tougher. 4-speeds with traction definitely will stress the rear more than automatics. You can install a B-body (1965 preferred) in a A-body very easily. I've done it. All I did was oval out the "eye" hole on the leaf mount. Worked perfect and looked better (notice how dusters give a "backwards" 3-wheeler look from the rear??). It will also give you the 4 1/2 inch bolt pattern.
I don't think that was a real good example of a 8 1/4 holding up under power....he said it was a mild 318, so probably 180hp ish. Also, 4 speed + power + 8 1/4 + sticky tires = broken parts....either the 4 speed will break, or the rear will break.....and yes, I know, I must be some sort of mathematical genius to come up with that formula...
.Seriously though, if you are planning on racing quite a bit, unless you are a die hard 4 speed guy (and very skilled) I would seriously consider switching to either a 727 or a 904. They are easier on the drive train, and WAY more consistent...and consistency wins races. Just food for thought.
j par
Well-hung Member
The 8 1/4 is is out of a Dodge Dakota 1988? I think? A B-body is probably going to fit fine. The Dakota rearend is already a couple of inches wider. At the moment I'm still trying to get over the cost of the stroker !! When it's running and driving again, next week (i hope) i will have more enthusiasm about spending more.
j par
Well-hung Member
We sold the 727 that came with the car for $40. After all the research, time, work, and expense to put that 4 speed in, there'll be no way I'll consider a automatic! I'm a die hard 4 speed guy and (getting very skilled ! Lol).I don't think that was a real good example of a 8 1/4 holding up under power....he said it was a mild 318, so probably 180hp ish. Also, 4 speed + power + 8 1/4 + sticky tires = broken parts....either the 4 speed will break, or the rear will break.....and yes, I know, I must be some sort of mathematical genius to come up with that formula...
Seriously though, if you are planning on racing quite a bit, unless you are a die hard 4 speed guy (and very skilled) I would seriously consider switching to either a 727 or a 904. They are easier on the drive train, and WAY more consistent...and consistency wins races. Just food for thought.
in the end i just want to go out and have fun, I don't have to win. I will try and race a small 6 race series at Woodburn dragstrip over the course of this next spring and summer. Once a month. It's mainly to learn the basics. I'll try not to be to hard on the car.(but no promises!!! Lol )
WA71swinger
Well-Known Member
On a separate note. I bought a trailer this past year. Have 3 grand kids in Hillsboro. Been wanting to try out Woodburn. I'll have to see if your schedule is off a week from my points races schedule this year. I'd be happy to drop in and knock out whoever is giving you a run in the points. Feel free to be a spoiler at Renegade in WA.
Like someone posted above. Mild 318 (maybe 200-220 HP) rolling out of the hole on street tires. I'm about to put about 350-400HP to a set of Hoosier 26x8 slicks this year. Which reminds me. I need to post a wanted: 8 3/4 a body add.
j par
Well-hung Member
Oooo ! a ringer, I never thought of that? The race I'm going to enter at Woodburn is called the hole in the hood series. I think you'll have to have a tunnel ram or some kind of riser or something coming through your hood? I actually don't even have a hood on the car right now I just have a dual quad tunnel ram which I think will qualify me. I think the first race is 4/18/15.
doogievlg
Well-Known Member
I have a 360 that's around the 400 hp mark. I have a handful of passes at the strip on the car and a lot of street miles on the car with the slicks. I have a 8 1/4 with 3:55s and it is holding up great. I'm not sure at what rpm I launch but I had 1.9 60 ft times. On the street I am very rough on it too. It's not a four speed car so it's not as bad but it will give you an idea. That being said, if I was in your position I would save up for a Dana just to be safe and because you will want more power and you wolnt have to worry about your rear!
Btw stick with the four speed. It's much more cool to watch and a lot more exciting to race I am sure.
Btw stick with the four speed. It's much more cool to watch and a lot more exciting to race I am sure.
Pana.Mopar
Duster Down Under
I've been running 8 1/4 behind 383/727 for a few years now and never had an issue. It's got 4.10's and Sure Grip. I'll probably jinx it now but it's running fine. I've got an 8 3/4 at home that needs shortening and the like for when the 8 1/4 goes.
lead69
hopeless car junkie
It's not just about the horsepower but the torque you will be making and at a low rpm, adding that to a four speed and you will puke that rear, it's only a matter of time and traction. You can get decent money out of that rear now and put that cash into something better. There are a couple 8 3/4 housings on craigslist now and finding a 3.91/4.10 open center is not that hard, then just add a spool and axles from doctor diff. Sticky tires, big torque, four speed, c-clip 8 1/4 rear?, it doesn't add up.
WA71swinger
Well-Known Member
It's not just about the horsepower but the torque you will be making and at a low rpm, adding that to a four speed and you will puke that rear, it's only a matter of time and traction. You can get decent money out of that rear now and put that cash into something better. There are a couple 8 3/4 housings on craigslist now and finding a 3.91/4.10 open center is not that hard, then just add a spool and axles from doctor diff. Sticky tires, big torque, four speed, c-clip 8 1/4 rear?, it doesn't add up.
I will have to say I agree. Made a couple of calls to guys I race with. I had previously mentioned 1 with a 4 speed. I have to correct myself now. He is running just around 400 HP 340. He has a DANA, because... he spit up 2 8 3/4 rears in about 10 passes each. He even twisted mark Williams axles with the dana ( lemon twister on past time) launching at 5000 rpms. He is running 11's in the 1/4. This guy and one other I spoke to today have been racing Mopars for 30+ years. The other has has an 8 3/4 in his dart running 11's to 12's depending on which motor, no change in rear end since 1990. Both guys told me the same as we have been hearing here all day. I was told to skip the 8 3/4 and use the Dana 60 I have. For What its worth. apparently that manual tranny is going be much more destructive than an automatic when you grab traction with slicks. More specifically they said when you come off the line spinning a little and then grab traction, which is going to happen sometimes. I actually prefer just a little tire spin out of the hole, end up with quicker ET and higher MPH. Rear ends on the other hand, do not like it. From talking to them, both you and I are probably going to destroy our 8 1/4 rear ends with slicks at the track.
Looking at the combo's cam, your way under geared.
I don't know what you'll run but for certain, you'll be pulling a long ways after the strip.
I dont see 11's though.
Just something to think about...
If you sell your 8 1/4 while it is all in one piece you will get a decent amount of money out of it to go toward a Dana or whatever type of rear you decided to use.
If you take your chances with the 8 1/4 and it breaks, it won't be worth diddly squat, and you will have to by a new rear anyway. So if you think about it, you will save money by selling it while it still works....just food for thought.
Also, don't forget to put a rev limiter on your motor so if/when your rear does break you won't lose the motor too.
If you sell your 8 1/4 while it is all in one piece you will get a decent amount of money out of it to go toward a Dana or whatever type of rear you decided to use.
If you take your chances with the 8 1/4 and it breaks, it won't be worth diddly squat, and you will have to by a new rear anyway. So if you think about it, you will save money by selling it while it still works....just food for thought.
Also, don't forget to put a rev limiter on your motor so if/when your rear does break you won't lose the motor too.
j par
Well-hung Member
My trainer car with a 8 1/4 3.91 power lock.
440 with 150 shot.
All 3 kids learned how to race in this car.
Car is a 74 Duster.auto
Nice looking car ! ? Lol
j par
Well-hung Member
Whats your 1/4 mile time ?
Rocky_JS
'cuda
Yes, I go to a lot of swap meets, car shows but the track rarely. I go to Mopar day at Woodburn and that's about it for the track. I lived in Milwaukie for many years when I first moved up here.
The local shows run all summer long and normally kick off in April. Here is a link to the area events http://www.pdxcarculture.com/Events.aspx. Check back often as the list gets updated regularly especially this time of the year...
We have a local a-body group for support, parts, and meeting up and hanging out. It is a roster of about 20 or so folks. We meet up at Stark Street Pizza, 9234 SE Stark St. The last Sunday of EVERY MONTH from Noon to 3:00 P.M. So if you or anyone else wants to come on by, the next one is on Feb 22. All are welcome, with or without car. PM me your info name, email, etc and I'll have rick add you to the roster/mailer.
John
The local shows run all summer long and normally kick off in April. Here is a link to the area events http://www.pdxcarculture.com/Events.aspx. Check back often as the list gets updated regularly especially this time of the year...
We have a local a-body group for support, parts, and meeting up and hanging out. It is a roster of about 20 or so folks. We meet up at Stark Street Pizza, 9234 SE Stark St. The last Sunday of EVERY MONTH from Noon to 3:00 P.M. So if you or anyone else wants to come on by, the next one is on Feb 22. All are welcome, with or without car. PM me your info name, email, etc and I'll have rick add you to the roster/mailer.
John
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