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Thread: Fulvia Connecting rod sizing

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    Fulvia Connecting rod sizing

    Hello

    I am rebuilding a 1300cc Fulvia engine. It has new pistons and a new crankshaft (Broke the old one) and the mains are perfect and the cylinder wall clearance is perfect but I have run into a problem.

    The connecting rod spacing is a little out, about 0.004" greater than tolerance. On other cars that I work on like Alfa's and Maserati's I would just shave the bearing cap on the face where the bolt goes through, but on the Fulvia it has serrated surface on the face of the cap and you can't do this. On modern cars with fractured caps they actually have bearings that add in increments of 0.001 " to the back side of the bearing cap to close the clearance. But I don't think Lancia has this. I did purchase some first undersize bearings for this but they come in 0.010 which is to much. Short of buying new connecting rods does anyone have any ideas on how to correct this.

    Kevin

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

    Not sure which dimension you are talking about, and is it all conrods that have this problem. I have seen pistons too high on one side because the block was not bored correctly....

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    Re: Fulvia Connecting rod sizing

    That sounds like my previous block, awaiting the test results If the angle check on no.3 bore

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    Re: Fulvia Connecting rod sizing

    Quote Originally Posted by KLHarper View Post
    Hello

    I am rebuilding a 1300cc Fulvia engine. It has new pistons and a new crankshaft (Broke the old one) and the mains are perfect and the cylinder wall clearance is perfect but I have run into a problem.

    The connecting rod spacing is a little out, about 0.004" greater than tolerance. On other cars that I work on like Alfa's and Maserati's I would just shave the bearing cap on the face where the bolt goes through, but on the Fulvia it has serrated surface on the face of the cap and you can't do this. On modern cars with fractured caps they actually have bearings that add in increments of 0.001 " to the back side of the bearing cap to close the clearance. But I don't think Lancia has this. I did purchase some first undersize bearings for this but they come in 0.010 which is to much. Short of buying new connecting rods does anyone have any ideas on how to correct this.

    Kevin
    have you determined where the clearance issue comes from? is the crank under size, or the rods over sized?
    if it's the rods you may not have a choice but to replace them.
    bmarler/
    1967 fulvia sport zagato
    1961 appia vignale convert.

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    Re: Fulvia Connecting rod sizing

    Quote Originally Posted by bmarler View Post
    have you determined where the clearance issue comes from? is the crank under size, or the rods over sized?
    if it's the rods you may not have a choice but to replace them.
    It is the rods, as the crank is in perfect specification.

    I can't believe that Lancia did not have a way of altering these. Even with brand new rods you frequently run into this problem, especially from cars from this era.

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    Re: Fulvia Connecting rod sizing

    Quote Originally Posted by lancialulu View Post
    Not sure which dimension you are talking about, and is it all conrods that have this problem. I have seen pistons too high on one side because the block was not bored correctly....

    Uh it is the connecting rod big end to crankshaft clearance. I would be hard pressed to accurately measure 0.004 " piston deck height differences.

    Boring the block is actually quite simple, and it does not really matter if the angle is 10, 13 60 or 90. You are going to get your centers on 2 of the cylinders on one side and bore them and then rotate the engine the required angle and find the centers on the other cylinders and bore them. With the modern CNC boring machines it is more precise than when it came out of the factory in the 60's.

    Kevin

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    Re: Fulvia Connecting rod sizing

    Are you using plastiguage to measure. All my 1600s are at the limit but not worn so I just leave it and have a loose engine but still spec oil pressure. 1600 cranks are nitrided so do not wear. Are the crank journals to spec and does the rod hold the shells nice and tight?

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    Re: Fulvia Connecting rod sizing

    Quote Originally Posted by lancialulu View Post
    Are you using plastiguage to measure. All my 1600s are at the limit but not worn so I just leave it and have a loose engine but still spec oil pressure. 1600 cranks are nitrided so do not wear. Are the crank journals to spec and does the rod hold the shells nice and tight?

    I have not used Plastigage in 30 years, it is only a tool of the backyard mechanic, any serious engine builder uses micrometers, dial bore gauges, CCM and laser measurement. My accuracy is around +/- 0.000040" (0.001mm).

    The crankshaft is brand new and perfect. Nitride cranks do wear, the nitride just makes them more wear resistant. I have had to get many cranks that were originally Nitrided redone. My preference is to use Ion Plasma as it gives a deeper and more consistent case hardening, but I still use gas Nitride also.

    I do not build engines that are a "Little Loose". I only build engines that are as close to perfect as possible. They have my name on them and my reputation.

    I am uneasy about buying new rods and expecting them to fit perfectly. I have done engines for all the other Italian manufacturers and particularly on these older cars with NOS parts, they usually require a little work. The crankshaft on this car is brand new and was coated in a thick layer of cosmoline, and even it required a little clean up work to bring it within specs.

    It is normally a simple operation to bring rods into specs but these are a little different and I am not sure what to do. Right now I am exploring using Carillo rods, but that adds about 1200 USD to the bill, but I am still hoping that someone know a better way.

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    Re: Fulvia Connecting rod sizing

    as a serious engine builder you already know your options. if you can't re-size the big ends you either re-size the crank or replace the rods. i haven't heard of incremental sized shells for the fulvia, only standard over bore sizes. i would get a set of rods and check the sizing. send them back if they're not in spec.
    i haven't looked at the rod/cap interface on this engine, i find it hard to believe you couldn't re work that. you only need a couple of thou each side right?
    bmarler/
    1967 fulvia sport zagato
    1961 appia vignale convert.

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    Re: Fulvia Connecting rod sizing

    At the risk of entering into murky waters, here is a detail of the teeth in the conrod cap faces. This is from an 818.302 rod 2243315. There were some changes to these "dentatura" (lovely name) in later 1.6 rods. Use this with some caution, but perhaps its of help.
    Attached Thumbnails Attached Thumbnails Screen Shot 2018-06-22 at 4.39.45 AM.jpg  

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