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Question on timing belt tension.

Discussion in 'Boxers/TR/M' started by silvergts1998, Nov 17, 2007.

  1. silvergts1998

    silvergts1998 Formula 3

    Apr 10, 2005
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    Adam
    I was wondering when you put on a new timing belt, do these belt stretch alot where you have to retighten down the tensioner on a 512TR? I haven't taken mine out yet, but I think the 512TR tensioners are mechanical and not hydraulic right?
     
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  3. Newman

    Newman F1 World Champ
    Professional Ferrari Technician Consultant Owner

    Dec 26, 2001
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    Newman
    Its said on that once set you shouldnt reset it again. The boxer engine also grows more than the V engines do so a belt too tight can fail especially if you continue to adjust it. Mine were done in Dec05 and I havent adjusted mine since but I do reach down and give them a feel once in a while.
     
  4. Ricambi America

    Ricambi America F1 World Champ
    Sponsor Owner

    Adam -

    Read page B44 of the 512TR workshop manual I sent you. It has the specs, including the +/- tolerances.
     
  5. Meister

    Meister F1 Veteran
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    Apr 27, 2001
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    I've been told never to retension.

    That being said, I actually did a little R/R trying to find a squeal and replaced the new tensioner bearings with the old ones and then but the new ones back on as they weren't the source of the squeal....as such I retentioned my belts twice very within days of thr original change and have been running them for close to 3 years.

    I'm planning to change again in the spring as not to press my luck any further.

    Not recommending retension, just relaying a story.
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    Actually, there is no active tensioner, neither mechanical nor hydraulic, on the 512TR cam belts. The tensioners are mechanical spring-loaded devices that are rigidly fixed into position after the belt is installed (i.e., they never move after installation even if the belt stretches a bit).
     
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  8. carguy

    carguy F1 Rookie

    Oct 30, 2002
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    Jeff
    Wow tons if info already mentioned on this topic...isn't fchat great!

    Once the new timing belts and tensioner bearings are installed, let the "factory preset-loaded" springs "fire" the tensioners to take up the slack in the timing belts. The rotate the motor 2 revolutions....while closely watching the tensioners. The tensioners will fluctuate in/out slightly as the engine is rotated, due to the valve/spring actuations. On the 2nd-to-3rd rotation of the engine, watch the tensioners to see when they are at the point of most tension applied, this is the point at which the tensioner is most extended against the belt. When you reach this point, tighten down the bolt that goes through the center of the tensioner bearing....and that's it. A very easy procedure.
     
  9. silvergts1998

    silvergts1998 Formula 3

    Apr 10, 2005
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    Thanks for the info everyone! So there is no need to mess with the 10mm nut on top?
     
  10. carguy

    carguy F1 Rookie

    Oct 30, 2002
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    Jeff
    Nope....no need to mess with it. The spring inside the tensioner is "preset" at the factory for the proper tension. All you do is push on the 10mm nut to compress the tensioner inwards and release tension from the timing belt. So to remove the old belts, loosen the center-bolt going through the tensioner bearing and push in on the 10mm bolt as far as it will go....then hold it in this position and re-tighten the center bolt. Now you can remove the old timing belt, and tensioner bearing. Sometimes the old tensioner bearings must be destroyed to get them off, but most times they just slide off the tensioner bracket. Then apply some anti-seize to the tensioner bracket where the bearing goes, and slide on the new bearing. Then install the new belt with the teeth lining up to the old belts positions if your doing the mark-and-match method, loosen the center bolt and the tensioner will "fire" and apply the proper belt tension. Then crank the motor over 2 times by hand while observing the tensioner and lock it down at the point where it's applying the most tension (point of most travel against the belt). I hope this makes sense. Give me a call if not.
     
  11. silvergts1998

    silvergts1998 Formula 3

    Apr 10, 2005
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    makes total sense! Thanks for the advice.
     
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