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Thread: Question about Mark 8 ally control arm conversion

  1. #1
    Join Date
    May 2009
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    Brownsburg, IN
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    153

    Question about Mark 8 ally control arm conversion

    I have a pair of Mark 8 aluminum control arms that are almost ready to get installed. Before doing so, I took some measurements to compare the spring perch depth to the original SC control arms. I needed to figure out how it might affect my rear ride height. I'm hoping they can help lower the back a bit since the lowering springs I installed didn't lower the back as much as they should have. I digress...I noticed that base of the spring perch area of the Mark 8 and SC control arms are at a very different angle. The base of the Mark 8 perch area is about 25mm deeper on the inboard side than the same point on the SC control arm. The outboard side measures about the same on both. I used the arm mounting points as a reference, not the surface of the control arm.
    So, my questions to anyone who has done this conversion...does this cause any issues with the spring? Does it make the spring try to curve a little? Does anything need to be done to get that surface to have an angle more like the SC control arm? Does it change the ride height at all?
    I'd really appreciate any input that might save me from having to R&D the whole setup when I install them.

    Thanks

  2. #2
    Join Date
    Apr 2003
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    Ventura, CA
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    To do it right, you'll need to make or buy a perch for the spring, since the Mark 8 arms don't have one. Supercoupe Performance sells them.

    On my SC, I still had to cut 3/4 of a coil from each rear spring (Suspension Techniques) to get it to sit the way I wanted it to.
    Be excellent to each other.

  3. #3
    Join Date
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    Boston, MA
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    You can add poly IRS bushing from a 99-03 cobra energy suspension kit. That will raise it.

  4. #4
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    Imperial, MO (near St. Louis)
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    To truly "do it right" you'd machine a perch with a 5.5 degree taper. Nobody produces them any more though.
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  5. #5
    Join Date
    May 2004
    Location
    Va. Beach,Va.
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    I made some "economy" versions a while back.

    http://www.sccoa.com/forums/showthre...highlight=lcas
    SCCOA Member #2406
    '94 SC AUTO - 2.3 Whipple
    http://www.sccoa.com/forums/garage_v..._vehicle&id=19

  6. #6
    Join Date
    May 2009
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    Brownsburg, IN
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    153
    Quote Originally Posted by Mercutio View Post
    To do it right, you'll need to make or buy a perch for the spring, since the Mark 8 arms don't have one. Supercoupe Performance sells them.

    On my SC, I still had to cut 3/4 of a coil from each rear spring (Suspension Techniques) to get it to sit the way I wanted it to.
    Did you cut the spring to clock the spring so the cut end would sit where it could help compensate for the angle difference or to adjust the ride height?

  7. #7
    Join Date
    Apr 2003
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    Ventura, CA
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    1,893
    To adust the ride height. That said, my car is lighter than most, so that may have had something to do with it as well.
    Be excellent to each other.

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