Big Single - 2 Speed Glide Project

Discussion in 'Member's Garage' started by Boll!, May 20, 2018.

  1. Boll!

    Boll! Well-Known Member

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    Thanks mate.
    The panels look ok, at a glance, they are a bit roughly cut, edges are not real straight but they serve a purpose and save some weight.
     
  2. jellybeans

    jellybeans Active Member

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    How did you make them?
     
  3. Boll!

    Boll! Well-Known Member

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    Na, I didn’t make them, the fella who I bought the shell off had them made up somewhere.
     
  4. Boll!

    Boll! Well-Known Member

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    OK, So it was alive, Key word here - was.

    This is what went down.
    Car started, and was idling at around 1300 ish, for about 3-4 mins, was idling rich and spitting a little fuel out the exhaust, was not noisy but could have had a bit of lifter tick present.

    Then - Timing belt broke :( WTF, and for the life of me i can not figure out why- Gates racing timing belt by the way.

    Nothing stopped suddenly, crank still rotates freely, and all cams still seem to rotate well, i have not taken the cams out yet.
    The cams were degreed using this guide
    http://www.twinturbo.net/nissan/300zx/forums/main/view/1124020/A-guide-to-VG-cam-degreeing.html

    I counted and double counted timing belt teeth when i fitted it.

    I cant see anywhere where the belt has rubbed on or grabbed.

    The engine seemed to rotate without any tight spots when i had rotated it by hand when the belt was fitted.

    I would love to know any thought or ideas around the matter.

    A couple of thought i have are:
    When i adjusted the belt tensioner, if i made a mistake with that and was tensioned too tight, would that itself have enough pressure to brake a belt?

    Maybe i somehow damaged the belt when fitting it?

    Could the belt have been a faulty one?

    The timing belt was new, but was probably 4 ish years old, i wouldn't have thought they would have a shelf life though.

    Anyway, thanks for reading and look forward to some ideas.

    Cheers.
    Col
     
  5. jellybeans

    jellybeans Active Member

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    That sucks. After all that custom fabrication i bet you were not expecting problems from the standard parts.
    i don't have any specific advice other than i have had a few issues with stored toothed belts. We run several on each set up and must carry critical spares. By the time the belts in use break and are replaced with the belts in storage, being the same age, they often break within a week or so. Rubber we want to look after is kept in an air conditioned rubber room.

    MRc Dyno told me 2 weeks ago he doesn't like Gates belts as they can transfer/ deposit material onto the cam wheels.
    He prefers Nissan.

    None of this helps you though but age could be a factor. I think you bought this motor so not sure if you know the history of that particular belt . Have you inspected the belt for cracks, cuts, brittleness. Bend it back on itself and also look closely at where it let go. Put one end in a vice and put a come-along on the other if you have a load cell you could test the breaking strain. If you can determine that the belt is suspect it might narrow down your investigation.

    Best of luck that's really disappointing.
     
  6. Boll!

    Boll! Well-Known Member

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    So after the above shit show, 16 valves replaced and really still none the wiser on why the belt broke.
    But what i did notice was that when i pulled the tensioner off, the little tab that the M6 (i think) screw goes in to push the tensioner back had broken off, maybe that got jammed between the belt and something, there was some weird marks on the inside of the oil pump crank gear shield that may or may not have been caused by that little tab getting dragged through there with the belt.

    Anyway, its all back together and was started again, now there is a leaky cam seal, on the passenger side intake cam, there was a steady stream of oil running down the plate that bolts to the head behind the cam gears, no big deal, ordered some seals, replaced all of them while i was going, re assembled and still a leak, but very very little, just enough to make a mess.

    I though this was pretty strange, possibly damaging 2 seals on the same cam? doubt it.
    there were no marks or gouges that i could see on the cam or the seal housing so it has me stuffed.

    I decided to clamp the timing belt to the other 3 cam gears and try to take that 1 gear off by itself without jumping teeth, which worked well.

    When i got that cam gear off i was looking at where the seal was running, and it seemed the rear of the gear was only going into the seal by about 2mm so was only engaging the dust ring of the seal.
    I got a stock intake gear and done some measurements, and the stock gear would have had another 5mm of material going into the cam seal :confused:
    So i welded the centre of it to make it solid, fitted the stock welded cam gear and guess what, no leaks!

    This makes me wonder if the JUN cam gear was had a fault in the manufacturing process, and if my other intake cam
    gear is the same and will also start leaking.

    I have a couple of quick videos of it idling, but have no idea on how to post them.

    IMG_7300.JPG

    IMG_7301.JPG IMG_7303.JPG IMG_7304.JPG IMG_7305.JPG IMG_7306.JPG
     
  7. jellybeans

    jellybeans Active Member

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    getting closer.
     
  8. Boll!

    Boll! Well-Known Member

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    Yeah, but there is always something. ;)
     
  9. rob260

    rob260 Moderator Staff Member

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    Interesting find! Hope that does the job.
     
  10. MagicMike

    MagicMike Moderator Staff Member

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    S1 and S2 cams/gears are different aren't they? That's why JWT sell adapters depending on the combination used? From memory they are about 5mm thick. May or may not be useful, not sure what combo you are using.
    [​IMG]
     
  11. Boll!

    Boll! Well-Known Member

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  12. rob260

    rob260 Moderator Staff Member

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    The cam gears are different but you’d know if they were mismatched as the sprockets would be out of alignment
     
  13. jellybeans

    jellybeans Active Member

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    So what is happening with the JUN gears? Can’t imagine they were cheap. Not saying it’s the case here but a lot of aftermarket components just don’t have the overall quality control you would expect.
     
  14. Boll!

    Boll! Well-Known Member

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    Is there series 1 and 2 cam gears Rob?
     
  15. Boll!

    Boll! Well-Known Member

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    To be honest, I have no idea
     
  16. rob260

    rob260 Moderator Staff Member

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    For intake gears only
     
  17. Boll!

    Boll! Well-Known Member

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    Good to know
     

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