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Installing Con-rods onto a crank.

Discussion in 'Technical and Troubleshooting Torque' started by L0Ki, Nov 19, 2008.

  1. Ok First hickup in putting a motor back together. I took the conrods off without marking there location. Speaking of which what can i use to mark things in the engine?

    Now i need to put them back on. Whats the proper way of doing this? Do i need any special tools or anything?

    Thanks heaps.

  2. Do you have the service manual for the engine? How much machining work has been done on the engine? New pistons? Crank ground? New bearing shells? Have the pistons been off the rods? All relevant details. If the pistons have not been taken of the rods, you should be able to at least figure out which way round they go from the pistons (if they have some sort of ID marking on them) If you have not had any machining done, you could measure the crank to bigend clearance and install for the best clearances achievable.
    A torque wrench and new rod bolts/nuts are advisable (I'm assuming your engine runs a plain bearing crank). Proper torque values should stop any mischiefs occuring
  3. Are any of the rods different in any way at all? e.g. do any of them have pin-holes near the big end? If they are all completely identical there should be no problem, but it's not unusual for one or two rods to have an oil-way or something similarly obscure to ensure that wrong placement results in a bang, hahaha. But assuming no rod is different and the crank journals have been ground to the same size, which is the logical way to go, it shouldn't matter where they go

    Once you've got the rods sorted (an if any are different, consult a higher power), put a light layer of oil on the bearing surfaces (the journal and inside the concave of the shells), clamp the big-end over the journal and tendion the nuts to the torque dictated by the factory manual. REMEMBER - you should ALWAYS replace the bigend nuts, and if you can, the bolts, with new items.
    This might seem a bit naive, but I assume the nuts aren't a castellated type? They'd be self-locking correct? Castellated will require a bit more work.
    Incidentally, what are the rods made from - alloy or steel? If they're alloy you should check them very carefully and give them a very good polish.
    Also, if your motor is 'car-type' in having a crank-hanger, you need to fit the pistons and rods in the cylinders before you attach the crank - but you'd have noticed this on disassembly so nevermind.

    good luck, and let us know how you get on

    p.s. you can write on parts with a felt-tip pen provided the surface is clean. if it's a polished/smooth surface the ink can wipe off very easily so keep an eye on it