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The Use Of Oversized Lower Cam Outer Bearings?

Discussion in '308/328' started by dave80gtsi, Nov 23, 2019.

  1. dave80gtsi

    dave80gtsi Formula 3
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    #1 dave80gtsi, Nov 23, 2019
    Last edited: Nov 23, 2019
    The recent number of discussion threads here concerning the replacement of the pair of outer sealed lower cam bearings has twigged a vague memory that I have.

    I recall reading 'someplace' long ago of an individual or firm who concluded that these sealed bearings were a weak point in the engine design, as (per their thought process) they are under a far greater and more prolonged side axial force than the bearing manufacturers might have envisioned. Their solution was to machine the engine front case (into which these bearings reside) to a larger bore diameter, which then permitted the use of a larger, and assumed to be more robust, sealed bearing.

    However, a Search here, as well as the greater internet at large, has struck out.

    I'd be keen to review this information again, so to review the pros and cons of the conceptual idea.

    Might this ring a bell with anyone who can point me in the right direction?

    Thanks - DM

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  3. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Have you done a search on the later 308QV/328 larger outer bearing size "SKF 630647" (special F only) for those threads (and the threads they reference)? Seems like a huge amount of work for not much benefit -- but JMO.
     
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  4. dave80gtsi

    dave80gtsi Formula 3
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    Steve - Thanks - I've been searching all morning! And in so doing, I find your post no. 26 in this thread: https://www.ferrarichat.com/forum/threads/cam-drive-pulley-bearings.581890/page-2

    So it seems that the early QV's (and perhaps going back to the 2 valves?) had 40 mm O.D. Bearings, which were 'improved' to a 44 mm diameter for the later QV's, right?

    Thus, one might therefore see a benefit for a 2 valver to machine the case so accept the newer larger bearing?

    Thanks - DM
     
  5. Rifledriver

    Rifledriver Two Time F1 World Champ

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    The later bearings did last longer but are a non standard size and a lot more expensive. The 40 mm bearings did a great job and really are very likely to only need to be replaced once or twice in the life of the engine provided good quality parts are used. Replacing the outer bearing, the only one that really wears out is a simple job. Does not really make sense to me to take the motor out, apart and perform the conversion for such a small benefit.
     
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  6. Steve Magnusson

    Steve Magnusson F1 World Champ
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    #5 Steve Magnusson, Nov 23, 2019
    Last edited: Nov 23, 2019
    Yes, a benefit, but it's not like a bunch of late 308 carb, 308i-2V, and early 308QV are having a huge problem in this area with the 40mm bearing. This change hits me more as a slight improvement that they were implementing into the 328 design and realized that they could put it into the late 308QV production too without a lot of grief/effort rather than being a change to address a critical problem. Are you having a specific problem in this area?
     
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  8. Rifledriver

    Rifledriver Two Time F1 World Champ

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    At this point in the cars life and the amount the fleet as a whole is driven I suspect seals are probably going to get hard from age and require replacement more than bearings wearing out and replacing one means replacing the other anyway.
     
  9. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Didn't that happen already about 15 years ago ;)

    I meant more is he having a specific problem that isn't just a normal wear/tear/service issue.
     
  10. Rifledriver

    Rifledriver Two Time F1 World Champ

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    No question and why we need to adjust our focus from wearing out to aging out.
     
  11. JCR

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    PM Scott McGehee aka smg2. I remember that thread you were talking about.
     
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  13. dave80gtsi

    dave80gtsi Formula 3
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    #10 dave80gtsi, Nov 23, 2019
    Last edited: Nov 23, 2019
    Thanks for the hint - perhaps this is the thread I might have been thinking of: https://www.ferrarichat.com/forum/threads/3-93l-4v-engine-build.444116/

    Copied quote from Scott as found in noted thread: The front timing registry is also modified to receive a bigger double row bearing vs the single of the stock setup, the new bearing can withstand more thrust loading and axial loading without fatigue and early failure of the oem one.

    Reason for the inquiry is that I do not recall having heard that these bearings have an unusual high rate of failure, and thus wondering if an upgrade could be justified at the next belt change?
     
  14. Rifledriver

    Rifledriver Two Time F1 World Champ

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    #11 Rifledriver, Nov 23, 2019
    Last edited: Nov 23, 2019
    They don't and the water pumps are not too small either. The bearings only have a high failure rate when poor quality bearings are used or if belts are habitually over tightened. In 40 year of professionally repairing Ferraris I can count on my fingers and toes how many bad lower drive bearings I have replaced. That includes engine overhauls. If someone has done more they are doing something wrong.

    The front covers are machined to a specific block. They are not interchangeable with any other block.

    You are trying to fix that which is not broken.
     
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  15. dave80gtsi

    dave80gtsi Formula 3
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    Got it, understood. Thank you for your comments!
     
  16. derekw

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    I looked at changing to the bigger bearings but the earlier timing covers don’t have enough metal around the 40mm bearing. The best bearings I found were NTN 6203LLUA1C4 with L627 grrease (Mobil Polyrex EM, -20F-350F!) I found them from a Toronto supplier (ontariobelting.com) for about $16 and about $18 at my local bearing shop
     
  17. Hinecker

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    Hello all,
    Why don't you use SKF Explorer bearings? My 328 uses the 44mm odd sized and expensive bearings...I could only find them made by SKF.

    Just my opinion

    John.
     
  18. Martin308GTB

    Martin308GTB F1 Rookie

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    I had the whole bearings job done during winter 1998/1999 at 85.000kms by an official workshop for huge $$$$.
    Information on the www was sparse back then and FChat was just freshly launched IRRC.
    The engine came out, transmission separated and the drysump pump got dismantled. Reason for my badly leaking engine was the seal ring behind the outer bearing (I have the later design). Amazing. The inner diameter had shrunk about 1mm and had no contact to the shaft's sealing surface at all. Bearings were still perfectly o.k. :(
    With the informations a have today I would have saved a lot of money doing the easy job myself.

    P.S.: Repeated bearing failure might be caused by ignoring the fact, that you need C4 bearings down there. Some independent parts dealers don't even know about the differences regarding the bearing play classes.

    Best from Germany
    Martin
     
  19. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    Like tires.
     

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