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348 gear flanges

Discussion in 'Technical Q&A' started by troy_wood, Feb 10, 2009.

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  1. troy_wood

    troy_wood Formula 3

    Apr 28, 2007
    1,457
    Nova Scotia, Canada
    Full Name:
    Troy Wood
    #1 troy_wood, Feb 10, 2009
    I know I keep kicking this horse but its not dead yet for me.... Up to now the pulley-fence separation issues seemed to be confined to the drive pulley. But after reading the following post it would appear that 348 owners should have all fences tigged to the pulleys:


    Has anyone experienced this before? About 1500 miles ago, I had the belt service performed on my 1991 348. The mechanic had noticed that the belt had a crack in it while performing an inspection and recommended changing it to prevent a future catastrophe. On Sunday, I returned home from the lake (about 300 mile trip)and 50 miles from home, the car suddenly died. No real warning, about 15 seconds of a light "tink tink tink", and the engine just stopped. I returned the car to the shop yesterday. The mechanic took the cover off of the top of the passengers side driven gear and noticed that the "lip" of the gear (side closest to the firewall) was missing. There was a small, 3" ribbon of metal inside the cover. Needless to say, the timing belt skipped and I have X number of bent valves. I won't know for sure until the engine is pulled and broken open. If this has happened to someone else, please let me know what the root cause was. Right now the suggestion is just "bad luck". It is frustrating to have performed the belt service only to have this crater immediately after.
     
  2. Ricambi America

    Ricambi America F1 World Champ
    Sponsor Owner

    Dec 7, 2003
    16,467
    Winston Salem, NC
    #2 Ricambi America, Feb 10, 2009
    Mine cratered within 1000 miles of the major service too. There is some speculation that removal of the lower pulley ring nut, then re-torquing it causes strain on the pressed-fences. I don't know whether that's true or not, but I suppose it is possible.
     
  3. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    29,252
    socal
    #3 fatbillybob, Feb 10, 2009
    My guess it 2 bad majors. Ferrari has started using the resonance method to tighten belts presumably because it is more accurate. Just about everying prior to the 360 used the ferrari steager tensiometer which is 25+ years of wrenching on ferraris have never seen or held in my hand dispite how much I have been around the block. I suspect the belt tightening method or lack thereof. Fences do not see much force and some cars like the 550 don't have them on cam cogs at all. Ferrari barely tacks those things on there and has zero problems with them that I have seen even with really bent up looking ones that I have no clue how they could have gotten so bent up. Maybe the pros can tell you different. But my understanding is that if you got the belts riding on the fences for retention you got bigger problems. If you just drove the car for another 1500miles without doing the service I bet you would still have all the valves. That really sucks I feel your pain.
     
  4. troy_wood

    troy_wood Formula 3

    Apr 28, 2007
    1,457
    Nova Scotia, Canada
    Full Name:
    Troy Wood
    #4 troy_wood, Feb 10, 2009
    Last edited: Feb 10, 2009
    I should point out that this didn't happen to my car - it was a post I cut from another f-site. I should have put the story part in quotes...
     

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