Timing belt hanging over tensioner | FerrariChat

Timing belt hanging over tensioner

Discussion in 'Technical Q&A' started by Irishman, Sep 20, 2025.

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  1. Irishman

    Irishman F1 Rookie

    Oct 13, 2005
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    Raleigh
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  2. fatbillybob

    fatbillybob Two Time F1 World Champ
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    Aug 10, 2002
    29,297
    socal
    Install error. Without tension belts need to be fully installed on cams and tensioner with cams straight up on marks and #1 piston at TDC. Then tension belt. Then rotate motor in driven direction until you are back to #1 piston at TDC. Everything should look perfect and the motor spin easily and freely when doing this. 308 run best if cam timed but work just fine on assembly marks.
     
  3. Irishman

    Irishman F1 Rookie

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    Thanks, I agree. But where was the error?

    I installed the belts without tension. In fact, I would say it is impossible to install them unless the tensioner is fully compressed. The #1 piston was at TDC. All the cams were on the factory marks. The motor spins easily. And, in the picture, it is clear the belt is fully installed on the cams.
     
  4. tbakowsky

    tbakowsky Two Time F1 World Champ
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    Sep 18, 2002
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    Why is your exhaust cam pully so much further forward than the intake? At least thats how it looks in the photo. Could be a perspective thing, but looking at the stud, it looks to be not seated properly on the cam snout..
     
  5. Irishman

    Irishman F1 Rookie

    Oct 13, 2005
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    Thanks for the posts and private messages.

    The good news is that after a few engine rotations the belt is back on the tensioner. This happened getting the engine back to TDC.

    The bad news is I still have to take the whole thing apart. I discovered this morning that the exhaust pulley lip is cracked. It's not completely broken but I can pull the lip a little bit away. I would not want to roll down the road with it. Now I have to go find a pulley. I'll check everything carefully when I reassemble.


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  6. Ferrari Tech

    Ferrari Tech Formula 3

    Mar 5, 2010
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    I have replaced the pullies before with billet aluminum pullies offered from a respectable supplier. I had the center bolt leak oil from both cams on one bank. I finally found the aluminum was slightly thicker and didn't allow the o ring to crush properly. I ended up using two o rings stacked and this stopped the leak. Just be aware of the possible issue if you use aftermarket. I have used them more than once and only had the one issue. Just check it so you don't have to go back in a second time.
     
  7. Irishman

    Irishman F1 Rookie

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    Thanks, but I am not following. Probably me. I do not recall any "leak" in this area. The pictures are showing the timing belts which are outside of a fluid area.
     
  8. Irishman

    Irishman F1 Rookie

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    I am trying to find a replacement pulley.

    First outfit (which I trust) is asking me if my pulley is plastic or steel.

    Mine is plastic.

    My ignorance. Why is the vendor asking plastic or steel? Is it bad to mix and match?
     
  9. RedNeck

    RedNeck F1 World Champ
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    I'm guessing so they give you the correct one. Ferrari loves to change things mid year...If I remember correctly though, Hill engineering makes an uprated set of those. You'd be well advised to look into them before buying another Ferrari part
     
  10. windsock

    windsock Formula 3
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    Nov 29, 2006
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    Seen that many times, if these cars still have the plastic pulleys we toss them for aluminum.
     
  11. Martin308GTB

    Martin308GTB F1 Rookie

    Jan 22, 2003
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    You will probably hate to hear that, but when the lip of one of my pulleys cracked while doing a belt change I replaced all four. Because I expected the other three following soon with less luck and perhaps cracking while the engine runs. I purchased original Ferrari steel pulleys back then in 1998, because no aftermarket alternatives were available. They were big $$$$$$$ and the biggest challenge was timing while fiddling with the three holes for the pin. I wished, there were alternatives with five or more holes on the market, like available today.
    Or even seamlessly variable oblong holes. (In which I don't trust)

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    Best from Germany
    Martin
     
  12. Irishman

    Irishman F1 Rookie

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    I have been wondering about the timing. If I just use the factory (assembly) marks on the cam it doesn't matter, correct?

    I know the "right" thing to do is set the timing with a degree wheel. But it's been running great just using the factory marks.
     
  13. Martin308GTB

    Martin308GTB F1 Rookie

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    #13 Martin308GTB, Sep 30, 2025 at 9:57 AM
    Last edited: Sep 30, 2025 at 10:16 AM
    Yes, the timing marks on the cams are sufficient. But you will struggle anyway, because your replacements you will get are not, and cannot be exactly identical regarding the radial position of the holes for the pin. In relation to the belt tooth pitch.
    My fight took a whole working day (8hrs.). Maybe experienced pros are faster, but I regard this job as a major pain in the arse.

    BTW. I just looked into my records and compared the costs from 1998 for my steel pulleys with the damned three holes with the current price from Ferrari UK (Maranello Conc.) While I thought, the 1.600.00 DM for the set of four (former Deutschmark, now around € 800.00) were expensive, now the price did skyrocket. 312.00 GBP plus VAT / pc.
    I would have a closer look on the set from Superformance. Their set of four is around GBP 500.00 +Vat and they also have five holes. I have no experiences regarding wear of the aluminium though. But it's not so wear-resistant one might think. It's not much better than the GRP they used for the plastic ones.
    Maybe there are others here, who have long-term experience regarding the wear of the aluminium pulleys.

    Best from Germany
    Martin
     
  14. 2dinos

    2dinos F1 Rookie

    Jan 13, 2007
    3,070
    Just my opinion.....My 308 GTS has the plastic ones, my GT4 has the steel. I want to replace those plastic ones at the next service because they have visible wear, and I have seen those gear fences crack off on another 308.

    This was decades ago, and we bought replacement from the dealer. The replacement part was steel, and ~ $300 ++ for that one gear. We had the engine out, so that was much easier to access to set up timing etc. Looking back, I kind of wish we would have replaced the whole set (12-1600 $$). It was a buddies car, and he wanted to pump the brakes on replacing if the other gears were functional. We looked them over pretty carefully and pulled on the fences and didn't see any signs of failure so it was just the one. Maybe Eurospares has a good set of used steel gears??
     
    Martin308GTB likes this.

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