240Z, 260Z, 280Z Performance / Technical Discussions related to performance motor enhancements, upgrades.

Scored Crankshaft?

Old 12-16-2005, 08:16 AM
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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 keep the block and crank, and 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.
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Old 12-16-2005, 08:31 AM
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Is this an L24 or L28 motor? If you find that your crank is toast I have a spare L24 crank if you want it.
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Old 12-16-2005, 03:03 PM
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it's an L24, and you offered me the crank last time too...
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Old 12-17-2005, 08:55 AM
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Originally Posted by Fast240Z
it's an L24, and you offered me the crank last time too...
I thought so...well, I still have it if you need/want it.
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Old 12-20-2005, 10:02 AM
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I think your motor "stuck" because of water in the cyclinder does not compress. tapping it with the starter probably squeeze it past those leaky valves and rings. If your crank is scored it was likely already bad. I've seen several cranks in very good condition even after 150 k.
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