What would you like to chock that one up to?? When I bought my Z it had 82k miles on it and a knock in the #5 cylinder... =( Only mod was a Stillen Intake. Owner supposedly took good car of it, but when I did change the oil, he'd been using fram filters and castrol syntec in it... Could possibly be the problem, but Z's can spin bearings even without the pulley. I've had the pulley on my TT since I put the new motor in. Been in for about 16k miles. I've got both a lightened flywheel and an underdrive pulley... No issues... So... I'm not gonna argue it either way, just stating that a motor spinning a bearing at the 82k-89k mark isn't out of the ordinary... Are you the original and only owner? If not, maybe the previous owner didn't change the oil/filter every 3k and/or didn't use Nissan OEM filters and good oil? Never know.