Main Bearings and Crank Bearings, Need someone to double check my figures

[chicos240]

I am tearing down a block and getting it honed. I need help with my Main and Crank bearing calculations. Thank you for your help.

According to the FSM.The way to check what bearings you need is simple(roooight)

SO here is my CrankShaft and Block



Numbers on Block are 2 1 1 2 1Numbers on Crank Are 1 2 1 2 0Using the chart I get2+1=3 Yellow1+2=3 Yellow1+1=2 Green2+2=4 Black1+0=1 BrownSo for my Main Bearings I need Yellow/Yellow/Green/Blue/Brown

Now For my Crank Bearings I need the lower numbers on the crankwhich are 1 2 2 1According to this tableI need 1 Black 2 Brown 2 Brown 1 Black
Modified by chicos240 at 5:40 PM 1/10/2008

[Hijacker]

Word to the wise. If you call up Nissan and ask for crank bearings, they will give you mains. Call them rod bearings I asked for mains and it took a minute of decoding for him to understand I meant crank bearings.

For crank bearings just ask for the crank bearing pack. It's cheaper than buying individually and it should include a thrust bearing. Every dealer I"ve talked to sells them for about 45-50 bucks for the back, but want 15-20 per bearing, plus 25-30 for the thrust bearing. The only downside is that it seems nissan sells the pack with all thicknesses the same instead of giving you the thickness options.

For Rod bearings, you're right on the money. I've never seen them sold as a pack, so you'll have to order them individually. Which is better anyways as the road bearings see more load than the main bearings.

[Slipstream]

I went with aftermarket bearings and measured everything out instead of using the stamped number way. I think the pack of ACL bearings cost me around $90 for main,rod, and thrust together.

[chicos240]

Roger that..... ROD BEARINGS it IS!Question on buying the pack.IS there not a reason for different thicknesses? WHy would nissan sell them all the same thickness? I am assuming if you do not use the right numbers you are going to install the wrong size Rod Bearings and be out of SPEC and then when you hit 300 HP things will break.

[chicos240]

Where did you get your bearings?

[Slipstream]

I bought mine from Zero-Lift. I had machined my block, polished my crank and went with eagle rods, so I wanted to make sure everything was within spec. The fsm has all the specs and where to measure it all.

[Hijacker]

Nissan's range of thicknesses isn't really that big of a deal. The range from thickest to thinnest is like .005" at best I think.

The coding system is to help the bearings stay on the tighter side of the tollerances I believe. But you'll be well in spec with a set of bearings. So long as you haven't had your journals machined or your crank turned.

EDIT: I pulled the bearing sizes. The grade 0 spec is 1.977mm~1.980mm and the grade 6 spec is 1.995mm~1.998mm. That means the wiggle room between tightest bearing and loosest bearing is .021mm That's pretty tiny IMO.

[Hijacker]

Booya. I was bored at work this morning, so I went ahead and translated the bearing chart for the Main Bearings



Now you can see all the different grades and their thickness specs.

I did a quick conversion of the tightest and loosest spec.

1.977mm = 0.07783"1.998mm = 0.07866"

That's barely a thousandth of an inch difference between the tightest and loosest bearing.

[drifter_for_life06]

is this for S13 SR's as well?

[Hijacker]

That chart is straight out of the 1991 180SX service manual

[Hijacker]

Update! I just received my Main Bearing Pack set from Nissan, and the reason they were all the same grade was because they were oversized for a machined crank. To order regular bearings, you need to order them individually from the chart, which is expensive. I've seen them anywhere from $16-$20 per bearing pair.

[Hampshaa]

Sorry to thread jack.

I'm building a bottom end as well. My problem is I had the crank polished due to some grooves on every journal ( it was not undersized just polished). since their was metal taken off the journals can I still go by the numbers on the block and crank? Will it still be in spec? If not could I theoretically order the tightest tolerance OEM bearings and be within spec since the diff grade tolerances are so small?

[Hijacker]

With the polishing, you'll have to plastiguage the crank to make sure that whatever bearings you have are in spec. I would think going with the thickest bearing will help tighten it up, especially if they didn't remove any measurable amount of material.