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mondial timing belt change

Discussion in 'Technical Q&A' started by srephwed, May 1, 2012.

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  1. srephwed

    srephwed F1 Veteran
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    Apr 29, 2012
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    fred brown
    #1 srephwed, May 1, 2012
    my first ferrari a mondial 4 valve is on it's way to me.i am giddy with anticipation.i am however not even going to attempt driving the car untill a timing belt and tensioner replacement is done.i have read some threads that discuss the belt being loose then tight in spots.if i am reading instructions correctly that actually should not happen.the procedure says after proper installation and timing of the belts you rotate the the engine untill you find the spot where the spring load has the tensioner extended the most and lock it down.in effect the spring is adjusting the tension at a point where the belt is as loose as it will be then after tightening the spring is no longer a factor.thanks to everyone for your input.i can see already this is a very good board to be a member of.thanks again,fred
     
  2. PT 328

    PT 328 F1 Rookie
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    May 1, 2005
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    #2 PT 328, May 1, 2012
    You are correct, this is a great community. I am not sure if you have seen these reference resources for the timing belt change so here you go.

    www.birdmanferrari.com

    and the technical threads noted as a sticky at the top of the 308/328 section.
     
  3. srephwed

    srephwed F1 Veteran
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    fred brown
    #3 srephwed, May 1, 2012
    yes i have seen those instructions.i have actually printed them for reference during the job.the one question that i had was about the job of the tensioner.when i see it and actually do the job i may get a better understanding of the tensioners job.i can't imagine that he tensioner would be moving in normal operation.the up and down revs would have it dancing all over the place.thanks again to all
     
  4. docmirror

    docmirror Formula Junior

    May 6, 2004
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    Ft Worth TX
    #4 docmirror, May 1, 2012
    I'm going to cause some controversy now. I know everyone has an opinion but my take is that the belt is installed at TDC (PM1-4) and the tension lock nut is tightened gently. The engine is then turned two full revolutions back to TDC, then the lock nut is released, and then tightened at TDC. This sets the preload of the spring tension on a cool engine as it was designed at the factory. Moving the belt to a position where it is under strain from the combined effect of the lobes of the valves may put too much pressure on the system when warm.

    Note that our engines grow as they heat up, and since this is a system with no floating load like modern timing belts, getting it too tight is much worse than too loose. I've done 8 cars this way so far, all with Hill bearings and no failures, not even any problems. YMMV.
     
  5. srephwed

    srephwed F1 Veteran
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    fred brown
    #5 srephwed, May 1, 2012
    i see what you say about too much tension.an aluminum block grows a great deal more than the normal cast iron.have you noticed when you did this procedure while rotateing the engine would the belt seem at times floppy? the timing belts in reallity are like a roller chain.like you stated a little loose is much better than a fraction to tight.thanks,fred
     
  6. docmirror

    docmirror Formula Junior

    May 6, 2004
    781
    Ft Worth TX
    #6 docmirror, May 1, 2012
    I never move the engine with a loose tension bolt, so I can't tell you if it flops around. The only reason I run the engine around twice is to let the belt true up on the pulleys. After the belts are both on and tight, I do one final check, and run the engine for a few seconds then shut it off and visually recheck everything once more.

    Put your location in your profile, maybe you are near someone and can have an assistant over when you start your job, and before you finish just to have a second set of eyes on the work.
     
  7. Glassman

    Glassman F1 World Champ
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    #7 Glassman, May 2, 2012
    There will always be a postion where the belts are a little loose.
     

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