Maesuring chain tension | FerrariChat

Maesuring chain tension

Discussion in '365 GT4 2+2/400/412' started by Arvid, Apr 7, 2014.

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  1. Arvid

    Arvid Formula Junior

    May 28, 2012
    668
    Norway
    Full Name:
    Arvid Andersson
    #1 Arvid, Apr 7, 2014
    Last edited: Apr 7, 2014
    In my search for timing perfection I have pulled of the front cam covers,exposing the upper chain drive. The chain looks to be in good condition and so does the tensioner with no signs of wear at all. Both actually looks like new so they can't have run that many km's. Good news :)

    I'm reading the WSM for backup as I go along and fig.54 section B52 dictates that the tension between cam pulleys should be 20kg for 1mm play in the chain.

    At firts,checking tension on my chain,I thought it to be correctly tigtened with maybe 3-4mm play. But reading B52 made me wonder... Should it really be that tight ? Only 1mm play when compressed by 20kg ?
     
  2. blkprlz

    blkprlz Formula 3

    Mar 24, 2007
    2,169
    Tampa bay
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    Bruce
    #2 blkprlz, Apr 11, 2014
    I'd be more inclined to tension the chain as decried in the WSM, that is to tension it until you get the described noise, then back off until the noise disappears. Then I'd measure the deflection with the amount of force, & note that.
     
  3. Arvid

    Arvid Formula Junior

    May 28, 2012
    668
    Norway
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    Arvid Andersson
    #3 Arvid, Apr 11, 2014
    Thanks,that is what I intend to do. The WSM describes the procedure well but I am puzzled over the high tension over the cams. Thought this would aquire to high stress over the tensioner and early wear...
     
  4. DaveO_48

    DaveO_48 Karting

    Jul 29, 2013
    184
    Henderson, Nv
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    David Odland
    #4 DaveO_48, Apr 12, 2014
    When checking the amount of slack in the chain, one needs to understand that between the two cams on one bank, there is torque applied to the sprockets by static pressure at the tappet when the cam is opening or closing valves. this twist makes it difficult to get a true deflection reading. A better location, but difficult to assess, is by reverse rotation of the engine by hand to take out all of the slack and then turn the crank forward only enough to unload and then tighten the pressure on the chain in the opposite direction. Best readings would be found where the adjuster is located. As the adjuster isn't spring loaded, excess slack should be evident when this process is performed.
    There seems to be no definitive foolproof way to provide maximum life from the adjuster, which, along with correct cam timing, is the point of the whole process.
    Harley Davidson v-twins have a similar disintegration problem. Which is only resolved with changing to a gear drive system, or frequent rechecks of the tensioners.
    Same design, same problem. Bad design, more expensive repairs for happy dealers.
     
  5. Arvid

    Arvid Formula Junior

    May 28, 2012
    668
    Norway
    Full Name:
    Arvid Andersson
    #5 Arvid, May 3, 2015
    Restarting this topic since I am in the middle of this adjustment in a couple of days. Knowing that the correct described tension according to WSM will result in a bit premature wear,I can't help asking if it's advisable to loosen the chain more than the manual precribes.

    Is there room for loosening the chain further than the 1/4 turn recommended and still not get the rattle ? This would leave the tensioner and pads a bit more relaxed and would result in a longer lifespan but I'll leave it alone if its not advisable for other reasons.

    A
     

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