Rod Bearing Clearances Tight

[rmlamp]

I need some input on my rod bearing clearances. I'm rebuilding my engine and am to the point that I'm checking clearances. I bought all the correct bearing grades from Nissan and am checking clearances for peace of mind. It's done the exact opposite. All the main bearings checked out and were all within spec according to the FSM. I am using a plastigauge, which i know is not the "preferred" method but should be giving me pretty accurate readings. The plastigauge is brand new and I was doing the reading around 80 degrees. When I got to the rod bearings, I got a reading of .001" or about .025mm on ALL rod bearings with almost no difference between them. The FSM shows standard clearance of .0011"/.028mm minimum. I've had a couple people tell me that as long as the crank hasn't been machined (it hasn't) and I've selected the correct bearings (I have), then it should be good to go. I also took the crank to a local machinist and had him check it, everything checked out. Is this something I should be majorly concerned with? Is there a possibility that the factory bearing grades are not usable on this engine?

[ca18det_boy]

That's pretty close man. Personally, I would go with the FSM. So I would double check the clearances one more time and then if you're still out I would order/exchange the bearings. .003 is a super small amount, but nissan engineers know a whole lot more than I do.

[rmlamp]

That's pretty close man. Personally, I would go with the FSM. So I would double check the clearances one more time and then if you're still out I would order/exchange the bearings. .003 is a super small amount, but nissan engineers know a whole lot more than I do.

Totally. What I'm struggling to understand is, all the bearing grades are the correct grade according to the marks on the block, crank and rods. This should mean (in theory) the clearances are all set back to when the engine came from the factory. I just don't want his thing to s*** out on me.

[ca18det_boy]

From my experiences there's never a set size on the bearings. So lets just say you order a grade 2 bearing. The allowable tolerances for said bearing will be .247-.253. I would still exchange them out for another set and just keep going until it matches what the FSM says. I know that "technically" it should be the bearing that Nissan used to assemble it initially, but the FSM trumps what was used. The other option is to go back to the dealer and talk with a good parts guy and get the sizes for all the different bearings grades, then you can order a set that will work with your application.

The numbers I just used were completely fictional and used only for an example. I don't know exactly what the tolerances are for that bearing. However, if you go to ACL, King, ect then they'll show you what tolerances are their standards for a standard and oversized bearings are.