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timing chain adjuster

Discussion in '365 GT4 2+2/400/412' started by SouthJersey400i, Feb 19, 2014.

  1. squidmark

    squidmark Karting

    Sep 11, 2011
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    Howard Dent
    When I rebuilt my engine, I used the time honoured method of 'if it feels right, it probably is right' - I found that whilst setting the cam timing I merely tensioned the chain until there was no slack when you reversed the engine ie turned the crank anti-clockwise after having turned it clockwise for a couple of rotations. With my nice new chain the tensioner adjusting screw was virtually hanging out! I then ran the engine in on the dyno (no chain noise) and re-torqued the heads (probably not necessary I know) and re-tensioned the chain when the engine was back in the car (whilst the engine was idling); as has been suggested, when you 'over adjust' the chain it gets noisy (I tried that!), so I backed off a turn or so from there. I hear what is said about the weight and deflection theory as told in the manual, but that would be virtually impossible once you've run the engine as you would have to remove the chain covers thus disturbing the 'o' rings so you'd really have to remove the cam covers too!
    Personally I think tensioning the chain after an initial run is a good thing - but rather tricky to use anything other than the 'noisy when too tight' theory.
    Conversely, on an old engine you would merely tension the chain to get rid of the noise, and if you run out of thread or it stays noisy - it's engine out time...
     
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  3. blkprlz

    blkprlz Formula 3

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    #77 blkprlz, Apr 10, 2014
    Last edited: Apr 10, 2014
    I should've suffixed that statement with :D as you are 'the' go to guy for NLA parts fabrication.
    Don't know if this would be worth your time since these are only used on our cars :(
    The tensioner pads associated with the chain are also hard to get but I seem to remember someone here fabricating those :confused:



    For once, the shop manual instructs a rather simple procedure (well, maybe not once) :)

    Edit:

    Just found who modified the material on the tensioner pads, Boyd Bowdish (b3tech).
    He estimates the lifetime with this modification is well over 100K mi., & states that coupled with a new cam grind can yield up to 8K revs with these V12's :cool:
     
  4. rovexienus

    rovexienus Formula Junior
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    Jean-Michel Savary
    This is very interesting information, would you be able to share the contact for Boyd Bowdish (web site, e-mail)?
    The site b3tech.com seems unrelated to mechanical items.
    Thanks in advance.
     
  5. Ak Jim

    Ak Jim F1 Veteran
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    Dec 23, 2007
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    Is b3tech his FChat name?
     
  6. blkprlz

    blkprlz Formula 3

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    Yes :D

    You can search for him here:

    1.) Log onto Fchat.
    2.) Click on "Search" at the top left-hand side of the page..
    3.) Click on "Advanced Search".
    4.) At the top of that page on the right-hand side, you'll see "Search by User Name"
    5.) Enter "b3tech", then click "Search".
    6.) Look for the smallest # of replies to a thread, go to that thread & look for a reply from "b3tech"
    7.) Click on his name, a drop box will appear…you can choose "Send a PM" or Send an Email" :)
     
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  8. dstacy

    dstacy F1 World Champ
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    Or you could go to the top of this page and click "search" and the drop down will appear
    then click "members list"
    then click "search members" on the right side
    and enter "b3tech"

    3 less steps
    :D
     
  9. blkprlz

    blkprlz Formula 3

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    Good one Dave!! :D
     
  10. dstacy

    dstacy F1 World Champ
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    Just screwing with you Bruce :)
     
  11. Fritz Ficke

    Fritz Ficke Formula 3
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    Let's keep things in perspective. Ferrari is not stupid, the material they used on the tensioners is not different then every other contemporary car was using at that time. Toyota's and Datsun used the same stuff and had engines that would go over 150K miles on the timing chains and guides, it is not the material on the tensioner that is the problem, it is the length of the chain and the heavy stress that it puts on the tensioners and guides that is causing the damage. There is no magic pill, and if there was an amazing modern material ( I do not believe there is) that would last 100K on the tensioner you would still have to pull the engine and change the chain and valve guides, etc. and every thing else required in the 50,000 mile service that the engine design calls for.
    This series engine was the final and economical version of the Columbo V-12 and the short chain and guide life is one of the manifestations of that.
    They are great cars and wonderful fun, but they are what they are.
     
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  13. rovexienus

    rovexienus Formula Junior
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    Thanks for all this, I sent an e-mail to b3tech.
     
  14. DaveO_48

    DaveO_48 Karting

    Jul 29, 2013
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    David Odland
    Ferrari isn't stupid, no. Better material, yes and available for decades. Good old USA aerospace industry. Taking the engine out and apart, now we are closing in on the "Ferrari and stupid" thing. Just a bad design from a manufacturer that likes to build complicated, delightfully so, vehicles. They don't always get it right but the effort is well intended, from the design side.
    Many great designs are held hostage by managements desire to maximize profitability. When purchasing a new product how often do you do the cost projections for the life of the product. Not very, would be the predominant answer. So, controlling the initial cost, getting the product thru the warranty period, and then enticing the owner to replace the product is at the head of the wish list for automobile manufacturers. Ferrari isn't any different, maybe more egocentric, but still in it for the money.
    I'm still not convinced that this design defect was intentional.
    Retro fitting to eliminate the problem however, is desirable. If you had to tear the engine apart, wouldn't it make more sense to mitigate the problem for future use. It isn't visible so it doesn't affect the aesthetics of the design. If you intend to drive the car, as opposed to the "hanger queen" approach, wouldn't it provide more reliability? It won't make the refit more expensive. It provides a source of revenue for entrepreneurs who have like minded interests. How many reasons are needed to "break the mold"?
     
  15. Fritz Ficke

    Fritz Ficke Formula 3
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    Dave, There is no intentional design defect on these engines but there is a sacrifice on reliability on these engines for build economy.
    If contemporary wear material works fine for other manufactures it is not the material that cause short life span.
    I have no problem with modifying engines for reliability, I am only trying to temper this belief that a different shoe material will make up for a poor cam drive system.
    As for driving Ferrari's, I put over 22,000 miles on my 400I before I sold it.
     
  16. DaveO_48

    DaveO_48 Karting

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    We are on the same page all the way to "poor cam drive system". Maybe build economy is involved with more than the chain tensioner part of the system? However, once the type of cam drive had been chosen, it would have produced a more reliable product had the chain adjustment method been more vigorously researched during development.
    Now that the adjustment parts are becoming obsolete, revisiting both the design and what materials to use when fabricating replacements could produce a part that would be a "one and done" correction.
    These cars aren't driven enough to warrant more than one refurbish for this problem. No one wants to repeatedly repair the same problem because of a poorly manufactured part.
     
  17. DaveO_48

    DaveO_48 Karting

    Jul 29, 2013
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    An "out of the box" concept would add two idlers like the ones between the cylinder banks. One fixed where the fixed chain guide shoe is, and one hydra-mechanically attached where the adjuster is.
    The hydra-mech part would work like this. First, the adjuster unit would be attached with a spring loaded but captured primary adjuster shaft. To adjust the idler, engine off, release the bolt that has the adjuster shaft pinned in place. The spring would then force the idler forward to remove the slack. Secondly, the shaft would have an internal cylinder which applies dynamic pressure to the idler when engine oil pressure is present giving continuous but limited tensioning. When the limit of the hydraulic adjustment is reached, engine off, release the captured bolt, the idler moves forward driven by spring pressure, reset the bolt. Drive on!
     
  18. Fritz Ficke

    Fritz Ficke Formula 3
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    You realize you have described a typical oil pressure fed tensioner that has been in production for years.
     
  19. Ak Jim

    Ak Jim F1 Veteran
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    Sounds good but is there room in there for all of that hardware?
     
  20. DaveO_48

    DaveO_48 Karting

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    #92 DaveO_48, Apr 12, 2014
    Last edited: Apr 12, 2014
    Obviously. So the "research" for better alternatives wasn't vigorous. Of course we do not know about all of the engineering challenges that were solved successfully because there aren't problems surfacing post production.
    With all of the engineering and design time put into the evolution of this engine family, this problem should have been resolved, there were obvious alternatives available, and even with the knowledge that the chain tensioning was an issue nothing was done. It isn't a faulty ignition switch that was ignored, it probably didn't cause any catastrophic human events, but it was avoidable. Worse has been done to satisfy the "bean counters".
    This type of design could be fit into the space available with only minor machining, a change in the tensioner casting, and small tooling investment. The sprocket pitch length and bearing speed would determine the space requirements for the fixed idler which would be a direct bolt in replacement. A redesigned housing would be required for the adjuster. Access to engine oil pressure would have configured once the needed pressure requirement was determined. With the probability of miss adjusting drastically reduced, friction loading on link pins and rollers would decrease and chain life would be elevated to a level where normal chain stretch would not exceed limits for the useful life of the engine as a whole.
    Would you rather adjust this chain drive design or the one that was used?
     
  21. kaiser

    kaiser Karting

    Dec 17, 2011
    73
    johannesburg
    I think the problem is not necessarily just one of design, lot's of cars with chain drive uses some type of chain adjusters similar to this one.
    But if you look at some of the pictures, you can see the material has started to break up, and that most certainly can be cured by using other types of friction material.
     
  22. Fritz Ficke

    Fritz Ficke Formula 3
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    I and many others have asked the same questions that are being asked now and a search can yield a lot of answers to these same questions. Some of the answers are by very experienced Ferrari mechanics like 'Rifledriver'.
    http://www.ferrarichat.com/forum/365-gt4-2-2-400-412/245004-observations-new-ferrari-engine-assy.html
    'Rifledriver ' describes the superior and more expensive cam drive of the previous version Colombo v-12 engine used in the Daytona in the above thread.
    The thread below even has pictures.
    http://www.ferrarichat.com/forum/365-gt4-2-2-400-412/152480-daytona-400-engine.html
    This thread discusses tensioning method and chain life. http://www.ferrarichat.com/forum/365-gt4-2-2-400-412/96775-1984-400i-timing-chain-tensioner.html
     
  23. wrxmike

    wrxmike Moderator
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    With all the discussion regarding the chain tensioner in these engines, it's worth mentioning that the position of the the tensioner is on the unloaded side of the chain, not the tension (driven) side.

    The primarly purpose of the tensioner is to take up the slack of the chain on the overrun, when the engine is decelerating and the chain is unloaded, because if there's too much slack in the chain, the undamped whip in the chain could lead to it skipping a cam gear tooth on the overrun.

    The correct adjustment is achieved when the tensioner just contacts the chain on the overrun, (and the spring behind the tensioner is not fully compressed and has enough travel to allow the tensioner to gently press on the chain and respond to any movement of the chain.) When the adjustment is done correctly, the tensioner will do its job and last a long time as there is little force applied to the chain,

    This was alluded to in Rifedrivers post in 2006
    http://www.ferrarichat.com/forum/135628666-post2.html

    If the tensioner is set too tight, the tensioner will always press hard against the chain, and this wear it out quick smart. This is easy to do, because it sounds quiet.


    M
     
  24. DaveO_48

    DaveO_48 Karting

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    So,how loose would the adjuster have to be, not that one should try it, to get the chain to jump a tooth on the intermediate gear. From the geometry of the design picture, not knowing how much torque is required to pull the chain over the cams, it looks like it would have to be extremely loose or nearly never adjusted. Would the "chain slap" from a loose chain cause faster wear than a correctly adjusted chain? Would it be as bad as an over tensioned chain? Or, is the issue chronic over adjusting? Should the adjuster wear be blamed on the onerous instructions for adjustment? Maybe.
     
  25. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
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    I think you will find it needs to be tighter than that. I was one of the new guys when chains were on their way out for Ferrari but I still remember the old guys telling me to tighten them at idle until they started to make noise and let them off until the noise stopped. That equated more or less to what I said about chain rattle on overrun. I think you are underestimating the need to keep even the "SLACK" side tight. At high rpm a chain whips around a lot. It needs to not have much slack in it. All this needs to be done with a hot motor too. That big piece of aluminum grows a lot when it gets hot and translates into a much tighter chain when hot.

    But you are correct. Too tight is worse. If it isn't quite tight enough you will hear the rattle and then you can always tighten it a bit more.
     
  26. Rifledriver

    Rifledriver Two Time F1 World Champ

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    #98 Rifledriver, Apr 14, 2014
    Last edited: Apr 14, 2014
    To slip a tooth requires it to be so loose it would make some pretty bad noises. Two real dangers there and I have seen both. 1, and most chain drives are susceptible to this is the loose chain whipping around trys to saw through the castings somewhere. All the metal shavings are not a good thing either. Also a loose chain wears the sprockets out. Now you need a new chain and a set of sprockets.

    2 is in the C4/400 motor the chain is long enough that before it is even that loose if the motor is turned backwards the cams will retard enough it will bend all the valves.
    Seen it happen.

    Bottom line is relying on a tyro's understanding of the manual or internet information for an education in correct chain adjustment on an expensive and idiosyncratic motor is a bad idea.



    People think Ferrari manuals are to tell you how to fix their cars. That is wrong.
    They exist to remind those of us that know what the specs are. The assumption is made that we already know how. And I can tell you from personal experience that people at Ferrari got a fair bit of enjoyment from that fact.
     
  27. Rifledriver

    Rifledriver Two Time F1 World Champ

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    I just noticed reviewing this you mentioned at one point you were in the AMU. I had friends at the AMU but over on the rifle side at Benning. Always thought about trying for double distinguished but never devoted the time to do it. One of my shooting buddies was and always hated him for it.
     
  28. wrxmike

    wrxmike Moderator
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    #100 wrxmike, Apr 14, 2014
    Last edited: Apr 14, 2014
    Thanks for contributing to this thread, I hadn't considered the "growth" of the engine when hot as another factor in chain tension

    Worth highlighting, especially the last paragraph.
    M
     

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