ENGINE BUILDERS: Main and Rod bearings..what's the big deal???
 

So, to all of you who have rebuilt their motors or are in the process:

I have heard from a few of you that the main and rod bearing take weeks, sometimes a month to get in...WHY???!

I just mass e-mailed 10 different nissan part distributors, asking them the following:


"Hi
I am currently doing an engine rebuild on a 2004 350z, going with forged pistons/rods, and many other extras. Anyway, I will be in need of main and rod bearings next week; I’m just waiting on my machine shop to give me the sizes needed (as this is based off of the true actual measurements on the crank and the NEW forged rods that I will be using)
My question, Do you have multiple sizes of bearings in stock? If not, how long will they take to get? I would like to call in the sizes this coming Wednesday and get them overnight shipped out here to Albuquerque, NM.
Please let me know if you can help

Thanks,

TODD"


So, we'll see what kind of response I get, but can anyone give me a recomendation as to where I should plan to order the main and rod bearings from..cause I'd like to order them once I know the EXACT sizes (has to be obtained from the actual crank and the rods).

I plan on overnight shipping them here so I can get this motor rebuild completed!

Thanks for any comments, suggestions, or info you may be able to offer!

-TODD

I just did my build-up with the Pauter rods and just to check we got new versions of the same color codes that came out of the stock motor and stock rods. They worked perfect and were right within specs when we put them in the Pauters. Apparently the Pauters are manufactured to match the middle size of the 3 available rod sizes from the factory. Same thing with my crank bearings...fresh versions of the same color codes..perfect. If you have the crank polished then you will need thicker crank bearings because the crank diameter will be decreased.:) When I ordered mine...all were within the country somewhere (2 days)...except 1 color that had to come from Japan....2 weeks.:( Problem is that there are so many different combinations...no-one could ever stock them all...just look in the service manual.

i understand that the measurements or "color codes" have to come off of the crank itself???
what size bearing did you use for the pauter rods? would that be a universal thing for these pauter rods, or is one set of pauter rods gonna vary from the next??
which bearings did you need from japan? the ones for the crank? did you call all the distributors in the us before going that route? or did you take someones word for it?
just wondering, cause i'll contact 20 different distributors if i need to, just want to know if it will even do any good!

thanks for the imput!
todd

can anyone else share their story??? anyone who has DONE or going through a rebuild...i know you are out there

I haven't gotten there yet, but the bearings come in grades 0,1, 2, and 3 I think, the crank is suppossed to be stamped with the grade needed.

The codes for the main bearings and rod bearings come off of the block and crank. There is a selection table with directions in the factory service manual (Pages EM-101 to EM-104). There are only 3 bearing sizes for the rods...0,1, and 2. The crank has 1 set of letters and 1 set of numbers stamped onto the pulley end counterweight. My numbers said 2,2,1,1,1,1 .This means

Rod #1 has a grade 2 bearing (green)
Rod #2 has a grade 2 bearing (green)
Rods #3-6 have a grade 1 bearing (brown)

My Pauter rods had the same diameter opening as the stocks. This is because the stock rods are all the same....the only thing that changes is the diameter of the crank jounals. This is why there are only 3 bearing sizes.

For the crank main bearings there is a little more involved. The letters that I mentioned that are stamped on the crank said
S GHLN ( you ignore the 1st letter according to Nissan)
There are more letters stamped on the block.Mine said
SRMS U (you ignore the last letter according to Nissan)

You then have the crank letters of G H L N
and you have the block letters of S R M S

From the table you reference G vs S to get a bearing color 34
" H vs R to get a bearing color 34
" L vs M to get a bearing color 34
" N vs S to get a bearing color 45

So #1 color 34= blue upper + yellow lower
#2 color 34= blue upper + yellow lower
#3 color 34= blue upper + yellow lower
#4 color 45= pink upper + blue lower

When you order the bearings from Nissan they come in pairs. I had to ask for 3 sets of blue/yellow and 1 set of pink/blue. Hope this helps a little. If you can use the manual.

what about crank journal wear? Is it expected that you might have to step up to a slightly thicker bearing as the crank wears with age? This is one major area I really know very little about and I'd love to learn more from people with experience.

Todd, I would really suggest waiting until your shop tells you the bearings you need. If you look in the service manual, there are a dozen measurements that should be taken before determine which ones to get. There is a certain tolerance limit, and each rod/crank journal may be slighltly different. You just never know. The numbers stamped on the block are for stock rods and pistons and a perfect crank. Who knows if yours will exactly match. That is why in addition to the numbers, many engine builders will just "fit" the bearings themselves. I would hate to see you preorder all this stuff, and then have it be slightly off.

Dito.

My engine had 6000 miles. We took a shot and ordered new versions of the stock mains for what was in the motor when it was new. We checked the clearances with the new bearings and everything was perfect....maybe I got lucky. Same thing with the rod bearings....again maybe I got lucky but all the clearances were right where they had to be. You have to remember that there are no aftermarket bearings available yet for these motors. You're machinists have to start somewhere.....why not with the bearings that the stamped numbers call for. If they are a little loose then upgrade to the next size....especially if the crank has been polished because that will put you to the end of the available bearing scale. Polishing typically removes .002 to .003 from the journal.

You will see when you go to select the main bearings that there are 576 different measurement combinations. The mains have measurement criteria that vary by .0001 inches for each color grade with a total span from the 1st grade to the last grade of .0009...that's all. The Nissan specs for the mains are extremely small. I challenge any machinist to "fit" that.

Remember this is a forged crank and if the oil changes have been done you should have minimal wear. The crank floats on a coating of oil between the crank journal and the bearing. The only time you will get wear is on a cold start when there is no oil pressure yet and the crank is resting on the bearing due to gravity. With 6000 miles my motor barely had the coating removed from the bearing surface.

That makes sense, and honestly, that was the answer I expected, but it never hurts to ask. Thanks for the info.

No problem:)

wow...awesome info!
will the machinist be able to order the bearings w/just calling nissan? or will he need the service manual?

i don't plan on pre-ordering them, just wanted to be prepared when i do order...this coming wednesday ...
thanks for all the info!

Yes, as long as he gives Nissan the numbers off the crank and block.

Although i would recommend that you give your machine shop a copy of the service manual that deals with engine assembly/dissassembly.

wow...awesome info!
will the machinist be able to order the bearings w/just calling nissan? or will he need the service manual?

I would not let a shop that doesn't have the manual work on my engine, that should have been their first request from you if they did not have it.

come to think of it, the shop has the manual on a disk format