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A Timing Belt Thread But Different

Discussion in '308/328' started by Glassman, Dec 5, 2009.

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  1. Glassman

    Glassman F1 World Champ
    Rossa Subscribed

    Apr 23, 2002
    15,236
    Montana, Oregon, Hawaii
    #1 Glassman, Dec 5, 2009
    One question that I don't think has been discussed to the point of nausea, is timing belt tension. I thought it might be beneficial to have a discussion of tension methods that DIY owners have used. At least I sure would be interested.

    I know the pro's have technical procedures that they use and a sonic tensioner seems to be widely approved of. But what about the home mechanic who doesn't have access to this unit or the experience to actually use one?

    I have just recently replaced my belts with a lot of input from Varell. I used his suggestion for tension (I hope correctly) by locking the rear rotors with clamps. After the belts were on I turned the engine 8 revolutions with the bearing loose to make sure the marks had not moved. I then re clamped the cam pulleys with the engine at TDC and put pressure on the crank with a breaker bar to pull any extra slack out of the long stretch of belt before tightening the belt tension bearing. At this point I can twist the belt about 45 to less than 90 Degrees at any point of engine revolution.

    Has anybody just replaced the belts, turned the engine over a couple of times and called it good? Is that actually acceptable? It seems to be the method in the manual as well as most Internet write ups on the subject.

    Does anybody have any other step by step procedures they would be willing to share here?
     
  2. mike996

    mike996 F1 Veteran

    Jun 14, 2008
    6,872
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    Mike 996
    #2 mike996, Dec 5, 2009
    What's wrong with the method in the Ferrari Service Manual? Worked for them... ;)
     
  3. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,367
    NY
    #3 Steve King, Dec 5, 2009
    I guess I missed the point of locking the rear rotors? Is this to prevent the cams from moving (1-4) after you pull the belt? I assume then if this is the case you are not using a cam lock tool or device. I usually just use the OEM method and rotate the engine maybe 4 or 5 times and then just tighten up the tensioner. I've done this 3 times and have not had a problem yet. I can see turning the crank 8 times to see if the belts line back up but I never heard or thought of putting tension on the long part of the belt and then tightening up the tensioner. Next time I pull the timing cover I'll check for the 45* twist to see what I come up with.
     
  4. Glassman

    Glassman F1 World Champ
    Rossa Subscribed

    Apr 23, 2002
    15,236
    Montana, Oregon, Hawaii
    #4 Glassman, Dec 5, 2009
    Thats exactly why I am wondering. If you take the translation of the service manual liturally, you can often get in trouble. I know its translated Italian, but seems to have some Greek content also.
     
  5. Brian Harper

    Brian Harper F1 Rookie
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    Feb 17, 2006
    4,078
    San Jose area
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    Brian Harper
    #5 Brian Harper, Dec 5, 2009
    The 45* twist method seems pretty imprecise. The tension on the long run of belt will vary with cam and crank position. Plus I'm not a very strong guy and you might have Kung-Fu grip. What if I can't twist a limp rubberband 45* and you hand-bend rebar for fun? We will give very different impressions of the same tensioned belt. Are you going to use my results as a data point?

    Assuming that the spring in the tensioner has still got the "boing" it was spec'ed to have, the directions in the WSM will probably give the most consistent results across all installations with all installers without the aforementioned sonic testers, etc.
     
  6. FF8929

    FF8929 Formula Junior

    Apr 12, 2008
    799
    Livonia, Michigan
    Full Name:
    Fred Flynn
    #6 FF8929, Dec 5, 2009
    I thought that this HAD "been discussed to the point of nausea". But OK, we'll go on to the point of "the dry heaves" then. I used the factory method, but, noticed that as I rotated the engine, the tensioners would move in and out at various degrees of the rotation. I then tightened the tensioners at their maxium extension. FWIW.
     

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