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Thread: Fulvia Connecting rod sizing

  1. #11
    Legendary Lancista bmarler's Avatar
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    Re: Fulvia Connecting rod sizing

    as usual, the amount of information you've gathered amazes me.
    that's a great drawing geoff, i would guess that taking the time to set up to re-machine those ends would eclipse the cost of new rods.
    but if there were no other route that information would be priceless.
    bmarler/
    1967 fulvia sport zagato
    1961 appia vignale convert.

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    Re: Fulvia Connecting rod sizing

    OK I have been doing some work on this project and here is what I have found.

    Geoff you are correct that is what it looks like and hopefully you can appreciate the dilemma.

    Bmarler yes you are correct in that the machining operation gets interesting. I looked at this with a machinist buddy of mine and we think we can do it, but it turns a bit into a science project, and even if we did it I would probably mess up a couple of samples getting the operation correct and I don't have the samples to mess up. And we would spend a fortune in time.

    OK here is where it gets interesting. I contacted a few people who know these things better than I do, a couple in the US, one in England and one in France (No prizes at guessing who they were) and I found out some interesting things. One that those 4 years of French in High school and college have pretty much left me. But more onto Lancia. Lancia did in fact make incremental bearings for the production models. These came in .0025 and .0050 oversize. These were generally never available to the public. The reason is that Lancia did not want to throw out a bunch of cranks that were slightly undersized, and, as I have learned, they figured out that adjusting the connecting rod caps is not an easy task. And the thought process is that with the undersize bearings everything is within specifications, the customer will not really know or care about the undersize bearings and if/when the car needed a rebuild it would go to the first standard undersize of 0.010.

    What we thought was that my crank, which is brand new, was one of the undersized ones and perhaps that was why it was stuck at the back of some warehouse. A reasonable assumption given how rare that NOS crankshafts are, but I checked mine and it is actually correct and dead center in spec. One vendor has some .0050 mains and thinks that they have the same in con rod bearings, but I really need the .0025 in an attempt to make it work and they have not seen any in years.

    Other things I learned from a couple of vendors that surprised me. I was told that "These things eat con rod bearing, hey but don't worry you just drop the oil pan and change them when you hear a little patter, and use 20/50 motor oil unless really cold". My thought was "Really" I thought Lancia's of this vintage were supposed to be engineering masterpieces. I am a PE and I like to try to put myself in time period to try to understand what the engineers were trying to do at that time. Some of it is interesting but some of it I have to wonder what was going through their head and were they just trying to be different or have a good design, because some of the designs are just not well thought out. One of them being this bearing cap design.

    Ok where am I going now. I just don't trust using a used rod and I don't know haw good NOS rods are so I am leaning to just going to some Carrillo rods. This will eliminate the issue of sizing in the future but it will not fix an oiling problem, it that is what it is, that will extend bearing life. The rods are overkill and even though I am just going to I beam rods as opposed to H beams they should be good for at least 10K RPM's which this engine will never see. I am probably also going to send back the standard oversized pistons and go with some JE pistons which are lighter and I can go with a lighter wrist pin. These should all make the engine rev better, due to lower reciprocating weight, and last longer simply due to time marching on and better metallurgy and control of tolerances available now, and the lower weight of the parts actually puts less stress on the other components as long as we keep the revs in check. I don't know what to do to extend the bearing life and I am just assuming that it is an inherent oiling issue. I am going to check my passages and perhaps chamfer the oil holes on the crank in an effort to get better flow, but in truth I am not going to spend to much time on it.

    It is an interesting build

    Kevin

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    Senior Lancista impaw's Avatar
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    Re: Fulvia Connecting rod sizing

    Allora.
    1966 Lancia Fulvia "Bella"
    1966 Lancia Fulvia racecar
    1977 Alfa Romeo A12 truck ( for sale )
    1968 Ford Mustang ( for sale )
    1955 Lancia Aurelia B20

    www.flattjern.com

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    Legendary Lancista bmarler's Avatar
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    Re: Fulvia Connecting rod sizing

    i don't really think there's an inherent oiling problem. they do however have a tendency to run at low pressure at idle. my engine has about 75k miles on it and runs very quiet and has proper oil pressure. as long as you address the oil pump during rebuild, clean out the oil passages in the crank, you should have no oiling problems. and of course chamfering the oil holes is a good idea. if the crank/rod bearings fail prematurely it's probably due to poor maintenance or oil selection more than anything else.
    i guess though, with new rods you can try to tighten up the tolerances a bit, nothing bad about that. keep us posted if you don't mind.
    bmarler/
    1967 fulvia sport zagato
    1961 appia vignale convert.

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    Re: Fulvia Connecting rod sizing

    That's the first I've heard of Fulvia engines 'eating' rod bearings.
    Ed Levin
    Fulvia 1,6 HF

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    Re: Fulvia Connecting rod sizing

    News to me too.

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    Senior Lancista Bart Boosman's Avatar
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    Re: Fulvia Connecting rod sizing

    Con rod bearings generally last the lifetime of the engine, which can be in excess of 500k km.
    The first bearing to go is the center main, and that one can easily be replaced by dropping the sump. I suspect that this one wears due to starvation as it also feeds two big ends.

    Don't forget this engine was developed as 1100cc and 56hp, in which case all components last for eternity.

    My S2 1600 engine uses standard rods, standard bearings and a 'new', remachined crank (after dropping a valve at speed). I have the rev limiter at 7800 at which speed it produces some 155hp and today, 30k sporty km after rebuilt, I have no reason yet to replace this center main. These engines are pretty good!
    Last edited by Bart Boosman; 25th June 2018 at 06:34 AM.

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    Re: Fulvia Connecting rod sizing

    Quote Originally Posted by Bart Boosman View Post
    Con rod bearing generally last the lifetime of the engine, which can be in excess of 500k km.
    The first bearing to go is the center main, and that one can easily be replaced by dropping the sump. I suspect that this one wears due to starvation as it also feeds two big ends.

    Don't forget this engine was developed as 1100cc and 56hp, in which case all components last for eternity.

    My S2 1600 engine uses standard rods, standard bearings and a 'new', remachined crank (after dropping a valve at speed). I have the rev limiter at 7800 at which speed it produces some 155hp and today, 30k sporty km after rebuilt, I have no reason yet to replace this center main. These engines are pretty good!

    Bart

    Thumbs up, you got very good Power from Your rebuilt engine.


    Tor

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    Legendary Lancista bmarler's Avatar
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    Re: Fulvia Connecting rod sizing

    Quote Originally Posted by Bart Boosman View Post
    Con rod bearings generally last the lifetime of the engine, which can be in excess of 500k km.
    that's a pretty optimistic figure! i hope i could see that kind of durability. at the miles i drive it would take a century though.
    my old daily driver vw just past a similar milestone though. 300k miles and still going...
    really though, you think these could last that long?
    bmarler/
    1967 fulvia sport zagato
    1961 appia vignale convert.

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