Why is there an elaborate set of documentation on bearing selection based on markingson the crank and block
but yet when I look at my bearings all of them are grade zero. The charts suggest there should be grade 3,34 and 4.
I am lost.

 

In my limited experience with building race motors, the use of main bearing replacements id due to the need for rebuilding engine blocks and matching main bearings to the crankshafts available. If your VQ37VHR block uses grade zero main bearings, congrats! You got a block honed to perfect specs and Nissan engine QR installed the correct bearings to provide optimum clearances when it was new. If you're rebuilding your engine, the documentation provides guidance for engine builders to determine what to do when there is damage to main journals or a crankshaft bearing surface must be turned and polished to create a fresh surface for that main bearing. I hope you have the precision tools and experience to do this type of work.

 

I was wrong about the grade zero bearings. It seems all of the bearings are stamped with a similar number e.g jk20d.
However there some letters like A,B etc. A color is also present on some of them. I know the color gives the grade even though the same part number.
I have not seen any description of the marking on the bearings.

 

Despite my past experience with older Nissan race motors, I wouldn't want to attempt rebuilding a modern VQ motor knowing the tolerances involved. It sounds as though you are learning as you go, and have limited experience working on Nissan engines- am I wrong? Is there a reason you're not at least teaming up with a local engine or race shop to work on this build?