News

Timing belt walking 308 engine

Discussion in '308/328' started by snowsports1, Jun 29, 2020 at 4:29 PM.

  1. snowsports1

    snowsports1 Formula Junior
    Silver Subscribed

    Jan 31, 2013
    916
    UK
    Full Name:
    Brian
    Hi my engine has been completely rebuilt and the first start today I have noticed one of the cam belts is walking / tracking towards the engine. Suspecting it was a faulty cam pulley I have changed these and it made no difference. The only way I can influence this tracking is a shim washer under the top m8 bolt on the tensioner. Having tried various shims it requires only a very thin washer (0.15mm) however it is very hit and miss and I’m not convinced it won’t gradually track on the pulley. Has anyone else experienced this issue?


    Sent from my iPhone using FerrariChat.com mobile app
     
  2. flat-12

    flat-12 Formula Junior

    Mar 18, 2011
    294
    Germany
    Most common problems are caused with the cam shaft pulley, like suspected.
    There was a Service Bulletin from Ferrari because of the "plastic style pulleys", these should be replaced!

    I have also seen pictures of Ferrari 308 tensioners breaking (fracture); maybe the tensioner is slightly twisted.

    Did you change the bearing or have you changed the whole tensioner with the bearing?
     
  3. 4right

    4right Formula 3
    Rossa Subscribed

    I had the same issue and was told that it was being caused by the lower cam belt pulley bearings being worn.
     
  4. snowsports1

    snowsports1 Formula Junior
    Silver Subscribed

    Jan 31, 2013
    916
    UK
    Full Name:
    Brian
    I have tried two different sets of cam pulleys Ferrari metal ones and superformance aluminium ones so I am pretty sure it’s not them. The lower pulley has two new bearings as part of rebuild


    Sent from my iPhone using FerrariChat.com mobile app
     
  5. fatbillybob

    fatbillybob F1 World Champ
    Owner Consultant

    Aug 10, 2002
    18,549
    socal
    If belt walks something isn’t square.
     
    Saabguy and albkid like this.
  6. waymar

    waymar Formula Junior

    Sep 2, 2008
    988
    Northeast, PA - USA
    Full Name:
    Wayne
    FWIW I sent back a set of SF pulleys as the belt walked. SF sent the pulleys to the OEM and they gave me a refund. I am awaiting the credit now. The OEM Ferrari ‘Plastic’ pulleys are still good and they did not walk for me..... just saying....
     
  7. snowsports1

    snowsports1 Formula Junior
    Silver Subscribed

    Jan 31, 2013
    916
    UK
    Full Name:
    Brian
    today i have tried installing a tensioner of another engine. This didnt make any difference. So i have tried two different set of cam pulleys and another tensioner. so the only things left is bottom pulley or belt. has anyone had to shim the tensioner to make the belt run true? i haven't spoken to anyone who has done this.
     
  8. absostone

    absostone F1 Veteran
    Silver Subscribed

    Jul 28, 2008
    5,094
    Fchat
    would bad cam drive bearings do it? are they loose?
     
  9. derekw

    derekw Formula 3

    Sep 7, 2010
    1,087
    London, UK
    Full Name:
    Derek W
    Brian, Who rebuilt the engine? Any chance the timing cover was changed? It sounds like the lower pulley may be off but with new bearings it should be square (unless the cover was changed as they are machined with the block. Was the head skimmed? It too may not be square.
     
  10. Patrick Dixon

    Patrick Dixon Formula Junior

    Mar 27, 2012
    684
    UK
    The plastic pulleys develop cracks. Just saying.
     
  11. johnk...

    johnk... F1 Veteran
    Owner

    Jun 11, 2004
    7,962
    New England/FL
    Be careful I had a belt failure which appeared to be related to a drive pulley bearing starting to fail. The belt walked onto pulley fence and was cut, then failed.
     
    waymar likes this.
  12. flat-12

    flat-12 Formula Junior

    Mar 18, 2011
    294
    Germany
    There should be no need to shim the tensioner. Never had this kind of problem with 308 engines.

    But I have seen broken tensioners and broken cam pulleys (in person).

    The bearing of the drive pulley is tehnet thing to check, like johnk… said, this could be the reason.
    Not a common problem.
     

Share This Page