Question about piston and con rod alignment
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Thread: Question about piston and con rod alignment

  1. #1
    Fellow Frogger!
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    Default Question about piston and con rod alignment

    Hmmm.....Just removed the pistons and con rods from my DS 21 barrels and (aside from two broken piston rings) noticed that the pistons (all four) are not assembled correctly with reference to each other. Basically the pointed piston crown should be to the right if you are looking at the number etched into the con rod at the cap end. On my sets, one or other part has been rotated 180 degrees: the pointed piston crowns are on the left side if you are looking at the etched numbers. It's the same on all four.

    Because of where the spark plugs protrude into he combustion chambers, I'm assuming the pistons were fitted in the barrels the right way round (didn't notice when i took things apart), meaning that it's the con rods that weren't fitted as per the manuals and as Citroen intended. Does it matter? If not why would Citroen specify the alignment/ fitting?

    Are the con rods perhaps curved or shaped - maybe to favour the rotational direction of the engine?

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    Is the direction of the con rod on the crank perhaps important because the con rod end has been machined to match the crank?

    I'm not sure whether i should correct the mistake when i reassemble, or leave as-was on the grounds that mine have 'worn-in'.

    Any thoughts or advice please?

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    Fellow Frogger! badabec's Avatar
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    Hello, if you are replacing the main and big end bearing shells then assemble them correctly. If you are not, then still replace the bearing shells and assemble correctly.
    My conrods had markings on both sides. On one side, all the etchings were the same, on the other side they varied. No I didn't take a picture.
    I know you don't want to spend too much money. I would definitely have the journals checked and polished. It's not like a Ford Cortina where dropping the sump is easy.

    Peter

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    Cheers Peter.
    Yes - I'll be replacing the shells, so any matching of current shells to crank is irrelevant. Like you, I'm heavily inclined to reassemble it as citroen intended. Before I do that, I'm going to look very carefully at my conrods (after giving them a good soak) to see if they have markings on the other side.

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    Fellow Frogger! badabec's Avatar
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    Hello, ask Mrs Santa Claus for an Ultrasonic Cleaner, minimum 3 litre. You can tell her it will bring her jewellery up like new (and her glasses and false teeth )

    Peter

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    Fellow Frogger! Rob T's Avatar
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    Pistons typically have the wrist pin slightly off-centre. Done to reduce the side thrust friction on the cylinder wall. Don't know about the rods in this engine, but it is not unknown for them to be non-symmetric. The manufacturers know what they are doing when they write the manuals, so I would follow the instructions.
    jaahn likes this.
    Robert Thorne
    Brisbane
    Citroenless - for now...

  6. #6
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    Thanks Rob. I totally agree.

    Peter: I'm amending my Christmas list right now

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    Hi
    AS already said, the manufacturer makes the rules for a reason so why would you do it another way. Change them to correct way.

    Sometimes the rods are made to give clearance on the block or cam or perhaps they have a lube hole in one side for spraying oil as needed. Doing it right by the book never got anyone in trouble.
    Jaahn

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