| The crank: If I understood correctly, the #1 main bearing block journal is worn due to a bad bearing. Therefore you want to line bore the block to accept an oversized set of bearings. Understand that the block is line bored from the factory. When calculating bearing grades you denote the stampings on the block, and those on the crank. These stampings denote tolerance differences at each main bore, and at each crank journal. The total difference is what determines the grade or (thickness) of the bearing at that location. These differences are in .0001" increments.
So... you're considering buying a set of bearings that are all oversized to meet the exceedance you will create by line boring the main bearing bore. As you can see this only accounts for half the equation. You have not accounted for the differences in the crank journals at each bore for the block. Although Nissan line bored the block to begin with you can see that when they held tolerances to .0001" they still had to compensate the precision milling with differences in bearing thickness to make it perfect. If you re-linebore the block. You would have to re-mic each bearing journal and bore, then purchase each bearing oversized to meet oem tolerances. The way around this is to machine the crank again but we all know this isn't a good practice and has proven to shorten the life of the engine. The problem with just replacing that one bearing with an oversized bearing, even if you had to buy a set (bearings are cheap) you aren't certain if the worn journal is worn on center. In other words, it could have worn off the centerline of the crank even though the hole measures round. My advise for you so you could keep the same pistons and 4 rods. >Buy 2 additional rods and another block.< Get the block bored to meet the piston/wall clearance of the pistons you have in their current condition. Use the crank you have and buy the oem bearings for the crank and mains based on the grade chart in the FSM. In the end this will cost much less than beating a dead horse, your block, and will put you at the same end result. You should be able to use any oem unmolested block with any oem unmolested crank and grade match the bearing set to that combo. All blocks and cranks fall within a standard sizing set by Nissan during manufacturing. Good Luck
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