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Thread: Scored Crankshaft?

  1. #1
    Z lover Pir0San's Avatar
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    Default Scored Crankshaft?

    My block I have now had a head on it that had a crack in it that would let water seep into the cylinder and then down into the crankcase. Water and oil would mix, but the motor never officially seized. Before I realized it was the head and not the block, I had gone outside to start the Z up, and the motor would "stick", so to speak. The starter, which is new, would engage with the teeth on the flywheel but the motor would not turn over. You would hear a thud noise, and nothing else would happen. I would turn the key off, and then tap it back over, and after doing this a couple of times, the motor would start. I'm assuming the water in the oil was keeping the motor from turning over, because the water would get between the bearings on the crankshaft and cause the motor to "stick" (I had spun a crankshaft bearing on another block that I had because of the water and oil leakage issue). I have since then bought a new rebuilt head, put it onto the block I have now (which had water and oil mixed in it, but was not driven at all after the motor stuck like described above) and no water and oil mixed. The motor runs now, but has bad oil blow-by at the rings, so the motor is in need of a rebuild.

    Since there was water in the oil, and the motor "stuck" but turned over afterwards, what are the chances that the crankshaft is scored? I ask this because I might have access to another complete block (sans head, etc.) and would rather use another block with a good crankshaft than have to pay $400 to get my crank reground. If my crank is good, then I would use the block I have currently as my rebuild.

    I haven't pulled the motor out of the car to see how it is because I still want the car to be able to drive down the road if needed.
    -Jeremy
    '72 Datsun 240Z

  2. #2
    Semi-retired admin Arne's Avatar
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    I'd say it might be possible, but there is no way to know for sure until you pull it apart.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
    Car blogs - 240Z - Porsche 911

  3. #3
    Registered User texasz's Avatar
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    I have an L24 crank if you find that you need one.
    '70 240Z - HLS30-08215 - Production Date 8/70
    '70 240Z - HLS30-06293 - Rusty and has Identity Crisis (must have been wrecked and the back 1/2 sectioned in from a later car maybe even a 280Z)...PARTS CAR!
    '71 240Z - HLS30-018482 - Production Date 1/71,Corvette Yellow, driven under a 4Runner, bought for parts, hit lotto with parts on car, may fix and put back on road

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    Supporting Member ChrisA's Avatar
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    Hi Jeremy,

    Texas beat me to it but I've got two extra cranks if you needed one. One 71 and one 72.

    Chris A.
    1973 240Z HLS30-156693

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    Registered User jmanz6's Avatar
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    If you have to pay $400 to have your crank reground, you need to find a new machine shop. I payed $70 to have mine cleaned and ground. You won't really know until you look at it. The cranks are very strong and it's likely that it will be fine. It may only need to be polished and it'll be ready to go.
    72 240Z, SU, header, Tokico Blue Struts, Suspension Tech Springs, All new Poly bushings, 280Z Tach, Crane XR-3000 ingition, 4-speed, "poop brown" Work in progress. Website

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    HLS30165540
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    Jeremy,
    It doesn't hurt to have extra parts. If you can get the spare block for a decent price, go for it. Rebuild it, balance, paint, rings, bearings etc.. This way you will have a completely rebuilt engine. Then when you have time take the old block apart and see what the problem was.
    The 1973 240Z 165540 Slightly modified. L28, 5sp, cam, headers, MSD 6AL, power windows, power door locks, leather seats, custom this and custom that.

  7. #7
    beandip beandip's Avatar
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    Quote Originally Posted by Pir0San
    My block I a

    Since there was water in the oil, and the motor "stuck" but turned over afterwards, what are the chances that the crankshaft is scored? I ask this because I might have access to
    I haven't pulled the motor out of the car to see how it is because I still want the car to be able to drive down the road if needed.
    Most likely the reason of the lock up is water in the cylinder . The water wont compress . You can easily blow a hole out the side of the block trying to run an engine is this condition. As for the crank , now way of knowing if it is good untill you have it miked . The longer you wait the more damage will be done by the water in the oil .
    I'd rather die while I am living than live while I am dieing. CZC 1887 IZCC 12602 Member of NorthWest Z Car Club

  8. #8
    Z lover Pir0San's Avatar
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    Quote Originally Posted by Ed
    Jeremy,
    It doesn't hurt to have extra parts. If you can get the spare block for a decent price, go for it. Rebuild it, balance, paint, rings, bearings etc.. This way you will have a completely rebuilt engine. Then when you have time take the old block apart and see what the problem was.
    See, I don't mind having extra parts at all, but since I'm 19 and living with my father, it doesn't always work out that way. So far, I have 2 four speed transmissions, an extra complete block (original w/scored rod and crankshaft) and two e88 heads. My dad's not too happy.


    Beandip, when you say blow a hole in the cylinder, do you mean due to the water problems, or my oil blow by? There are no more water problems after the new head, but ring problems arose instead.
    -Jeremy
    '72 Datsun 240Z

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