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Thread: Newb needing belt help.

  1. #1
    Junior SCH Member
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    Dec 2007
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    Newb needing belt help.

    Hey guys,

    I stumbled across this forum after criss-crossing the net trying to figure out how to keep my GT from throw its cog belt.

    In short, I have a 2000 Mustang GT that we're doing a custom cog setup using a YSi. It's a two belt system like the 5.0's. The problem is that the belt walks slightly to the back at idle, right to the lip of the idler pulley that Lee at ASP made for us. The lip on the idler is shorter than the belt, so the belt rides up onto the lip slightly and stops. Once on the dyno and under load, the belt gets thrown completely off, landing in the same spot each time under the car.

    Lee has made another pulley with a taller lip. We're hoping that that will keep the belt from walking back further. That sounds like it should work, but I'm wondering if there is another underlying problem here that we're not seeing...???? Anyone??

    FWIW, I noticed the other day that the idler pulley is cocked VERY slightly downward (towards the rad). Would this be enough to throw the belt?? The blower pulled and crank pulley are perfect.

    Here's a vid of it idling. When the cam gets pans on the engine from the driver's side, you will notice an idler just below the blower cog. Although that's not the idler Lee made, that's the idler cocked and in question. I've done a bunch of searchs with valuable info on here. Does anyone have anything else to add? Any advice would be greatly appreciated!

    http://s123.photobucket.com/albums/o...cture002-1.flv
    '00 GT - Whored out.
    '06 G35 Coupe - Wheels only.
    '06 Trailblazer SS - Wheels & Bolt on's.

  2. #2
    SCH Moderator "SN Guru" speedytang's Avatar
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    The larger lip on the pulley is going to destroy the belt. The reason it is walking is because your not center. Idler pulley will cause this and most usually need to shim it on the 5.0 to keep the belt center.

  3. #3
    Junior SCH Member
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    Thanks for the reply. Are you saying that it's b/c the belt is NOT centered on just the idler or all the pulleys??
    '00 GT - Whored out.
    '06 G35 Coupe - Wheels only.
    '06 Trailblazer SS - Wheels & Bolt on's.

  4. #4
    Junior SCH Member
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    Dec 2007
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    Also, what's the best and most accurate way for your do-it-yourselfer to measure straightness?? Straight edge??
    '00 GT - Whored out.
    '06 G35 Coupe - Wheels only.
    '06 Trailblazer SS - Wheels & Bolt on's.

  5. #5
    SCH Moderator "SN Guru" speedytang's Avatar
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    Dec 2002
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    Your idler is causing the belt to walk. Verify with a straight edge for the crank and blower pulley but I am sure your idler is causing the belt walk.

  6. #6
    Junior SCH Member
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    Dec 2007
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    Thanks! Will look into it today and let you know how it turns out.
    '00 GT - Whored out.
    '06 G35 Coupe - Wheels only.
    '06 Trailblazer SS - Wheels & Bolt on's.

  7. #7
    Junior SCH Member
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    Sep 2011
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    my car does the same thing, 35mm cog. start it up, belt walks to the end of the supercharger pulley near radiator. driving me nuts!! waiting on the twin plate to come and see how that works out. where am i checking with a straight edge? down all 3 pulleys?? blower, tensioner and crank on the side. my tensioner pulley appears to slanted slightly but its a flat plate and bolted to the new ysi,should it be slanted in. is that causing the walk? do i shim the tensioner plate where it bolts to the head unit. thanks
    Last edited by violentmustang; 09-20-2011 at 08:44 PM. Reason: spelling

  8. #8
    Senior SCH Member
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    Oct 2005
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    Carroll
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    I have always clamped a strait edge to the crank pulley since its basically a fixed pulley. Every other pulley can be shimmed to match the location of the crank pulley.

    Unless there is a strut brace in place somewhere or super strong bracketry................belt tension, acceleration and deceleration of the engine will cause flexing of the supercharger bracket and causing the belt to walk.

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