Big end bearing shells for CX2400
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Thread: Big end bearing shells for CX2400

  1. #1
    1000+ Posts gerrypro's Avatar
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    Default Big end bearing shells for CX2400

    The crank is machined and I have received my set of +.25mm bearing shells from CX basis.
    I have one question however!
    The Big end shells that are pictured below are of a type that I have never seen before in a CX.
    The part number is correct and corresponds to the CX Microfish PDF.
    The question is which cap goes into the rod and which cap fits in the cap of the rod?
    All other CX big end bearings are as in the second picture and are plain surfaces on both upper and lower shells! I have placed a picture of the old shells for comparison!
    Please I do not want speculation, so if you do not know for sure please do not answer!

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    Cheers Gerry

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    Contented Peugeot Driver addo's Avatar
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    The grooved shell goes to the rod body. You should be able to work out why.

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    Yes that was my immediate thought when I opened the box. It stands to reason that the groove transmits oil to the gudgeon pin and this way it can do so for 180 degrees of revolution.
    Then I started to think twice. ( fatal tendency )
    The groove reduces the surface area on the thrust strokes and compression strokes. The more free running strokes of induction and exhaust are more lightly loaded.
    The original had plain bearings and they coped fine. The hole for the gudgeon pin lined up and got an extra squirt every time the hole passed the oil passage in the journal. This occurs twice on a CX as there are two oil feeds on each big end journal and pressure is sourced from the mains either side of each journal. The rest of the time there is still residual pressure to the gudgeon.
    This makes me think that the plain shell will handle the major pressures more easily!

    Then, why have a groove relieved shell in the cap?

    The only justification that I can come up with is that it would provide an extra well of oil to assist with lubrication!

    Addo, what is your reason for saying that the grooved shell goes into the rod body?
    And I do not wish to appear rude but have you had a great deal of experience rebuilding engines?

    I read with interest that bearing manufacturers have experimented with Main bearing setups that employ a half grooved setup instead of the more usual full 360 degree grooving.
    Their reasoning was that this setup would provide better resistance to load than the standard arrangement.
    As mains receive higher loadings at the bottom of the journal these plain bearings are fitted into the bearing cap!
    That is the only information that I found concerning bearings that are half grooved
    Cheers Gerry

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    1000+ Posts gerrypro's Avatar
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    I have now had confirmation of my thought on the matter by two people who really know what they are talking about! These came through private emails.
    It seems I am correct in my assumptions. I shall now go ahead with the rest of the assembly!
    Thanks to all who responded!
    Last edited by gerrypro; 2nd April 2014 at 02:52 PM.
    Cheers Gerry

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    Contented Peugeot Driver addo's Avatar
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    So, you are saying the grooved half fits in the rod body, with the plain section in the cap?

    Perhaps it is worth forming a secret forum for people who do not wish to share information publicly.

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    1000+ Posts gerrypro's Avatar
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    Quote Originally Posted by addo View Post
    So, you are saying the grooved half fits in the rod body, with the plain section in the cap?

    Perhaps it is worth forming a secret forum for people who do not wish to share information publicly.
    No! The other way around!
    Cheers Gerry

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    1000+ Posts gerrypro's Avatar
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    One more detail --------I received an email back from Jochen Heusel today and he confirms my theories.
    Jochen owns CX Basis. I would recommend any one to deal with them, quick service and excellent customer support!
    Cheers Gerry

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    I have rebuilt probably a thousand engines of all different configurations during my time and a good many under warranty. So I think I know what I'm talking about regarding engine assembly. Believe me when I say, THE GROOVED SHELL GOES TO THE TOP. the idea of the groove is to supply the bearing surface and gudgeon pin with a good supply of oil at all times. [If your rods are hollow that is, and the pins are loose fit]. If the rods ain't hollow the shell still GOES TO THE TOP The oil hole on the old bearings doesn't lubricate the pin every 180 deg as you suggest, it lubricates it all the time due to bearing to shaft clearance, but this later grooved bearing provides greatly improved lubrication for the big end assembly and pin. The rod cap is only there to keep the rod in place, and is subjected to very small loadings compared to the top bearing, hence a ungrooved shell.
    Also, grooved main bearings have been used since Adam was a twinkle in dady's eye and the oil groove still goes to the top where the oil supply comes from to lubricate the shaft. put 'em in the wrong way and you'll run the risk of a main bearing flogging
    itself to death. The crankshaft loads are constant.
    Believe me I have seen just such a scenario on a 400hp V8 Mitsubishi diesel, stuck halfway up the Dividing Range with 28t of spuds behind him. And under warranty also [factory fitted the bearing upside down]. Remember GROOVE TO THE TOP.

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    Just an Inquiry for myself. Are the rods hollow? seems unusual that a "cheap" mass produced engine of this size would have such a feature. I would hazard a guess that the gudgeon pins are splash feed. Am I right?.

    Also on the bearings, check the back of the old shells, any signs of fretting [circular polished areas] then the rods should be resized because they don't have enough crimp tension. Same goes for the mains, any fretting and the block would need tunnel boring. My dad used to say "Do the job properly, or not at all". So expect a clip around the ear if you bodge it. Happy days eh?.

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    Quote Originally Posted by shanadoo View Post
    Just an Inquiry for myself. Are the rods hollow? seems unusual that a "cheap" mass produced engine of this size would have such a feature. I would hazard a guess that the gudgeon pins are splash feed. Am I right?.

    Also on the bearings, check the back of the old shells, any signs of fretting [circular polished areas] then the rods should be resized because they don't have enough crimp tension. Same goes for the mains, any fretting and the block would need tunnel boring. My dad used to say "Do the job properly, or not at all". So expect a clip around the ear if you bodge it. Happy days eh?.
    I have a NOS set of CX conrods, which are for an early CX. The factory manual has detailed diagrams on the engine bearings and also notes one machining operation to the edge of the small end boss is omitted for the 2400, so they seem to suit a 2200 rather than a 2400. These are externally identical to the conrods I have from a D Special / 21 engine. There is a drilling in the centre of the conrod and at the top of the small end. There is also a groove machined on the inside of the small end, behind the bush, to allow oil to pass around the bush and exit at the top of the rod. The bushes have a hole on either side (i.e. 3 and 9 o'clock), taking oil from the groove.

    The manual lists two grades of bearing. For recent PSA engines, there is a matrix for correct bearing selection, depending on the grade of the parts being used. Obviously, not as simple as just throwing in a set of shells.
    Last edited by David S; 5th April 2014 at 01:09 PM.

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    Interesting stuff about the rods. Obviously better engineered than I gave them credit for.
    Some engine manufacturers stipulate using bearings of a certain finished size and material according to a color code, or in some cases, a number on the crankshaft, or a single letter on the rods indicating finished size. Alfa twin cam comes to mind here but I didn't know Citroen bothered going down that road. Also interesting.

  12. #12
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    Quote Originally Posted by shanadoo View Post
    Just an Inquiry for myself. Are the rods hollow? seems unusual that a "cheap" mass produced engine of this size would have such a feature. I would hazard a guess that the gudgeon pins are splash feed. Am I right?.

    Also on the bearings, check the back of the old shells, any signs of fretting [circular polished areas] then the rods should be resized because they don't have enough crimp tension. Same goes for the mains, any fretting and the block would need tunnel boring. My dad used to say "Do the job properly, or not at all". So expect a clip around the ear if you bodge it. Happy days eh?.
    All good in that department.

    Also the rods are excellent quality. Very strong and made to very close tolerances. Have a look at the rods that are in the old long stroke D's. They are beautiful and quite innovative for the day w ith oblique cut faces that have to be angled towards the cam shaft side so that thrust from the power stroke is centred in the middle of the upper shell! No wonder all that TA boys want to update to ID/DS rods and get rid of the originals with babbitted bearings.
    Last edited by gerrypro; 6th April 2014 at 09:50 AM.
    Cheers Gerry

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    Quote Originally Posted by gerrypro View Post
    All good in that department.

    Also the rods are excellent quality. Very strong and made to very close tolerances. Have a look at the rods that are in the old long stroke D's. They are beautiful and quite innovative for the day w ith oblique cut faces that have to be angled towards the cam shaft side so that thrust from the power stroke is centred in the middle of the upper shell! No wonder all that TA boys want to update to ID/DS rods and get rid of the originals with babbitted bearings.
    The main purpose of this offset is to give the rod clearance inside the block. Yes babbitt bearings were a pain, much fitting by hand and all that shim cutting, mostly while lying on your back. Somehow I usually ended up lying on the tube of bearing blue. Not happy Jan.
    Having said that, I recall two identical air cooled diesel 3cyl engines, one made in Germany, the other made under license in Japan. The German had offset rods, the Jap had straight rods, [turns out they were from a 4cyl engine of the same manufacture]. The correct German 3cyl rods wouldn't fit into the Jap engine. And 4cyl rods could not be fitted into a 3cyl German. All other parts were interchangeable.
    Engine designers do have their little idiosyncrasies don't they.

  14. #14
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    Quote Originally Posted by shanadoo View Post
    The main purpose of this offset is to give the rod clearance inside the block. Yes babbitt bearings were a pain, much fitting by hand and all that shim cutting, mostly while lying on your back. Somehow I usually ended up lying on the tube of bearing blue. Not happy Jan.
    The original TA rods were actually wider across the journal than the DS rods that replaced them And as the Blocks were identical I don't think that they would have been worried about clearance within the crank case!
    I think they changed it just to go to a more modern rod and bearing set up than the original TA engines.
    Cheers Gerry

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    Perhaps for better heat dissipation, lower cost, longer lasting ??? in a higher performance of the engine. Looking at the DS parts book recently ... there are different ID rods, which will be important if making up sets. It seems the rods used in very late TA and early DS/ID were replaced from June 1957. According to the 1962 Slough ID parts listing, the difference is the waist thickness increasing from 19 to 22mm. So, one would prefer to avoid rods from an early DS19 or ID, although ID's that early would be exceptionally rare here. Anything originally from a later French or any Aussie ID should be the later type rod.

  16. #16
    1000+ Posts gerrypro's Avatar
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    Those early 19mm rods were first fitted into the 11D version of the engine and also into the 6H engine. The 6H I had was sold to Kim Harding! Its engine had been re-done, pistons sleeves and big ends. Kim pushed it too hard and threw a rod through the side of the block. Thankfully the present owner has had the block repaired ( through his Bus operator connections ) and has also upgraded the rods to the 22m thick variety!
    Cheers Gerry

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