First rb30 build, need advice

[Rileymax]

Just wanna preface this and point out I'm a mechanical fitter by trade but have had very little rebuild/machining experience, but I am keen to learn, hence this project. Bit of a write up here so bear with me, just want to make sure I do this right 

I've got an rb30e currently pulled down. Planning on putting a 25 head on it and running it in my s14. 

Not chasing huge power so I'm just going to try get away with factory bottom end for now. 

Started measuring the crank the other day, realised my budget daytona micrometer set wasn't up to the task (surprise, I know). They only measure to 0.01mm but the Nissan specs are to 0.001mm. Anyway, I started measuring anyway and came away with the mains being inline with the oem spec, as well as the big ends, except for no. 5. I consistently got a measurement of a hair over 49.96mm, where all the others were pretty spot on 49.97mm. The lower spec for grade no.1 is 49.961mm.

I'm getting access to some better gear my next days off to double check everything, but in the case that the big end is right on that bottom spec, is it pretty much just a case of straight to the machine shop for machining and oversized bearings? I understand I need to measure the tunnel as well to work out my oil clearance, but it's the different grade bearings in the manual that are confusing me. What is generally the process when one journal would still technically be in spec, but in a different grade? 

Thanks for coming to my Ted talk

[Duncan]

Well, if necessary you can mix and match bearing grades, that's what Nissan did from the factory (on rb26 at least)

However, the overall problem is no matter what you measure it as, unless you are totally happy with the result and put it together it will be going to a machine shop who will redo all the measuring anyway.

I'd suggest putting aside money for bottom end machining, and let the machinist decide the main and big end bearings. Also, you need suitable pistons for the hybrid engine and going oversize on the bore is the best way to ensure good clearances on an old or unknown engine.

Head is even worse, its worth getting that done while it is apart too. Certainly stem seals and cleaning and bleeding the lifters while it is apart is a good idea with an old head too, but also checking valve seat and cam tunnels