Are 8"'s strong enough?

Discussion in 'Technical' started by Bowtie, May 2, 2005.

  1. Bowtie

    Bowtie New Member

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    Hello Ford boys.:huh:

    I expect a little trash talk, but don't expect it from me I'm in your house. I have a 1963 Nova SS with a 74 mustang II front clip, and a 1973 comet 8" rear end and springs. This car was being built as a cruiser by previous owner, and now it's going the oppisite direction. My sbc makes 420hp/450lbs on pump w/o helpers. It's a street car that I drive to the local track. My current problem is the gear, I think it has 3.00's and is a limited slip. I'm turning 8.50's at 84mph, unable to get into my 3500 converter, turning 1.96 60's w/o tire spin and rpms to low to lock up the verter. I have a buddy with same car, same amount of power, but 12 bolt with 3.73's runing 7.70's So I plan on putting 4.11's in it, line lock and I know this verter flashes in at 3400 on that amount of torque. I run 26" slicks, is the 8" gonna handle that, am I on the ragged egde of what it can handle? I can sell this rearend to a street rodder, I don't want to start throwing money at it.

    Here's what I do know about the rearend.
    (these could be a digit off I did not jack up the car)

    Casting numbers: 670W
    4025A
    32
    DIF

    Tag Numbers: WDW-U 2HA
    3 00 6 521C


    When I spin one tire the other spins other way. I have tire shreds from burnout in both fender wells, have never asked anyone if they both spin.
    It leaves two marks on the road, right rear being darker than the left. I turn 2700-2800 rpm on 70mph highway running with traffic, and passing. I do not have speedo hooked up.

    PS, I drive a badars power stroke:cool:


    Here's a pic

    http://mysite.verizon.net/respfai7/sitebuildercontent/sitebuilderpictures/.pond/mvc-003f.jpg.w560h420.jpg



    http://mysite.verizon.net/respfai7/sitebuildercontent/sitebuilderpictures/.pond/mvc-009f.jpg.w560h420.jpg
     
  2. T.L.

    T.L. Banned

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    If your engine is really (and I mean really) producing 450 pounds of torque, then an 8-inch is not strong enough. 450 lbs. is 9-inch territory...
     
  3. 74merc

    74merc computer nerd

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    To quote a lifelong drag racer bud, 400hp with slicks, infinite with street tires.

    That being said, I'd get a 9 inch, 3.73s or better and slicks.
     
  4. Bowtie

    Bowtie New Member

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    Ok, I'll be conservative, and say 400hp/400lbs, still go with 9" ?
     
  5. Grabber75

    Grabber75 Member

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    9 inch with 32 spline axles......virtually indestructible. friend of mine has one behind his 454 and never had any problems with it. the 28 spline axles are weaker, which is what your 8 inch has also
     
  6. Jamie Miles

    Jamie Miles the road warrior

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    I'm really sorry, but your valve covers make me want to throw up. :biglaugh:

    (just messin with ya) :)
     
  7. Erick-Mav

    Erick-Mav Maverick Punk

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    Don't worry about it, the Ford 8" will probably break the Chevy engine. Also, there is no such thing as lbs of torque.
     
  8. Kilg0re

    Kilg0re Doh!

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    You can't be all that bad if your using Ford stuff ;-) Before to much longer I'm sure we will see Ford motor in there too hopefully... Welcome
     
  9. CornedBeef4.6L

    CornedBeef4.6L no longer here

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    My take on it is this. an 8 inch is good for about 300hp at the wheels with a stick and slicks. 350 with automatic. I am on my second pumpkin and this is the power range I am in roughly. Good Luck but I forsee a 9 inch in your future.:)
     
  10. MaverickGrabber

    MaverickGrabber MaverickGrabber1972

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    you can build the 8" to take it ....theres been a few thats ran them into the 10s
     
  11. Hawkco

    Hawkco Genuine Car Nut

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    May I say that you have decent taste for a Chevy guy. Though I am a Ford guy, I do love those Chevy II's. I always thought they, along with the Falcons, made the best sleepers.

    Since most of us hot rod guys never seem to be satisified and have the Tim the Toolman persona when it comes to power, I would go with a 9 inch rear because you will undoubtedly want to to go faster and quicker at some pont. The Ford 9 inch rear is by far the king of torque. A good, tough, bullet-proof 9 incher can be had from the guys who build the '66-'77 Broncos for off-road trail and rock climbing. Those housings are just 1.5 inches longer than your Comet 8 inch rear.

    Ever consider dropping a 514 (stroked 460) under the hood of that Chevy II? You can do it with that Mustang II suspension. :bouncy:
     
  12. littleredtoy

    littleredtoy Seth

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    I agree that an 8 inch can be built to handle most street car HP/torque.
    I am facing this dilemna myself in the future. 8 inch locker units and
    other pieces seem to be more expensive to me.
    It is going to cost me the same to take my stock 8 in. housing and add
    a new beefier 8 in. ring/pinion, locker unit, new seals etc. as to take
    a 9 in. housing that I have from a '71 Mach 1, cut it to fit, add a locker
    unit and lower 9 in. ring/pinion, new seals etc.

    I have priced it, 8 in. stuff is higher. Currie does make a heavy duty
    aluminum/alloy carrier for the 8's now.

    Check around at prices, but I agree that the 9 in. may be the way to
    go for your application. Keep in mind that the 8 in. is lighter and supposedly
    uses less HP however (friction).


    Seth
     
  13. Erick-Mav

    Erick-Mav Maverick Punk

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    Torque is measured in ft-lbs, Not LBS, which was my point. It was just a joke, I was nit picking at a very small semantic error because he has a Chevy guy and that's what we do to each other.
     
  14. don graham

    don graham MCG State Rep

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    i too think your on the ragged edge of the 8"'s limits. for your own peace of mind i'd go with a 9". i've got a 9" with moser spool and 33 spline axles and 4:33's behind my 302 and i'm confident that will be the last thing that goes. now that i've said that i'll be thinking of it at the track this weekend. (ha-ha). nice looking car by the way.:)
     

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