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    Timing Belt Horror

    Belt on left is brand new Gates T131RB 127 tooth belt.

    Belt on right is random 127 tooth. Was pulled from Das Beast. Motor literally ate half the width after 22 laps.

    WTF is up with our timing system? The belts are bar tight. Literally no slack. Things we will try:

    Replace Nuke cam gear with stock sintered gear

    New Z127 idler. (Old one was Z127)

    Thinner head gasket (0.040) MLS. OK since pistons are .020 below deck

    New belts. Trying 127 & 128 tooth

    Ideas?

    "And then we broke the car. Again." Mark Donohue, "The Unfair Advantage"

    1987 E30 3L Turbo Stroker Das Beast
    2002 E39 M5

    #2
    Originally posted by dvallis View Post
    Belt on left is brand new Gates T131RB 127 tooth belt.

    Belt on right is random 127 tooth. Was pulled from Das Beast. Motor literally ate half the width after 22 laps.

    WTF is up with our timing system? The belts are bar tight. Literally no slack. Things we will try:

    Replace Nuke cam gear with stock sintered gear

    New Z127 idler. (Old one was Z127)

    Thinner head gasket (0.040) MLS. OK since pistons are .020 below deck

    New belts. Trying 127 & 128 tooth

    Ideas?

    You didn't forget to tighten the tensioner (so that it won't tension any further) after a few hand rotations, did you?

    Otherwise maybe the timing gear. I have a nuke on mine and just pulled the head after around 600km and it looks fine, but you never know.

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      #3
      is the inside edge or outside edge worn? any witness marks on covers or other components? what crank sleeve are you running?
      89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

      new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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        #4
        Crank seal spacer was custom machined. Here's the diagram (key not shown)



        Will get back to you on wear marks. Everything is still filthy with oil and belt debris. :-) Pretty sure it was the outside that got ground off.

        Tensioner bracket seemed pretty loose, so I'm leaning towards that as the culprit. Would have let belt walk outwards.
        "And then we broke the car. Again." Mark Donohue, "The Unfair Advantage"

        1987 E30 3L Turbo Stroker Das Beast
        2002 E39 M5

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          #5
          yeah if the tensioner was loose then that is it. it just walked all over the place

          as long as you dont have the defective nuke gears youll be fine with it. the defective ones dont wrap correctly
          89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

          new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

          Comment


            #6
            I think you guys have it figured out- but just one more minor thing to confirm on reassembly: if the timing covers are accidently put on misaligned at the bottom, the belt will rub on those, even with perfect belt tension. Sent from my moto g(6) using Tapatalk
            (OO=[][]=OO) For Life

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