The Graded Bearing Debate ? Please Help Answer

[ZimNismoBoy]

OK so im here with loads of questions or should i say one big question.

So im getting ready to build my skyline engine with some good knowledgeable people at hand .

And there are some debates i have had with people some i have spoken to and some i have emailed and some messaged the list is endless.

So i am going to have a brand new N1 24U block from Nissan.

And a Brand new rb26dett crankshaft balanced and stamped with graded bearings numbers on the end !!!!!

So i have been asking the question for a while now and have not seen any core evidence.

Nissan makes graded bearings and installs these from factory .

They stamp the crank and the block with the bearing grades to be installed new from factory.

Nismo makes graded bearings which can be ordered for high performance uses.

Acl makes bearings in 3 different sizes ranging from STD to over size etc.

Then we have tomei who contracted acl to make bearings for them graded as well !!!!! suprise surprise, so why doesnt acl sell graded bearings ???? good question?

Now from what i have heard when builders talk of building they say put together a standard new crank with a standard set of shells from ACL.

Now nissan if they wanted to cut costs would install the same one size fits all type bearings per say for a NEW crank shaft to save time and money, but instead they install a graded bearing scheme that costs more in time and money then throwing in a standard size shell because of a known size on a crank ?

So why would nissan do this if they can save time and money ??

My question is if i am installing a new crank and block should i get graded bearings ? if not why should i get a STD set of Acl race bearings ?

Im sure these questions can be asked my many out there and im sure they are all also wondering so to help me out and get some ideas of the reasons behind all these methods please help out and try give me some insight ?

No flaming at my question and no asking if i had used search because i searched and searched and found nothing pertaining to the answer ?

Why does Nissan use a graded bearing scheme and aftermarket builders use a STD bearing scheme to build an engine ?

thankyou in advance ?

[The Dan]

Nissan grade their bearings because they want to save money. If you understand their process of assembly, you will understand why.

First of all, they employ dozens of people to assemble their engines and MILLIONS of dollars in machines which can tell them exact dimensions of a crank or bore. Can you imagine them having to pay for each person to hand assemble every engine one at a time? I mean, they hand assemble them but they don't sit there with micrometers or plastigauge and measure each and every bearing journal etc. Therefore, they stamp the crank and the blocks so that the person who does have to assemble it, can do so quickly and efficiently by grabbing the necessary bearings and just screwing it together. As long as the numbers match, they don't give 2/5th's of a shit what the clearance is because Mr Nissan already worked that out for them.

You may think ACL have taken the cheaper option by producing one-size-fits-all bearings but that is not the case. They spent a huge sum of money developing a bearing which has approx 40% higher load carrying capacity in a tri-metal bearing rather than Nissan's bi-metal design.

There is also the fact that as long as your bearings are all within 0.0002 of each other that it doesn't really matter. We never let engines go with a difference or more than that but usually due to ACL's fine engineering, we can be assured that they are usually all the same clearance, if not, within 0.0001 of each other. We have sent a few sets of bearings back to ACL for incorrect tolerances but in most cases we just keep them and buy another set when we are not happy. Every engine has slightly different characteristics, whether it be tunnel size or journal size, so we are never concerned about putting a set back into a box and trying another set as we know the next engine will probably use the set from the first.

My recommendation, whether using graded bearings or not......measure your engine before putting it all together. It's not worth the risk on your investment. It's like handing a stranger $10,000 and saying 'please take this money and invest it in what you think is the best return investment'

[T04GTR]

what he said.

when the cank is made and linnished its measured and given a grade. so when its assembled by the factory, they look at the grade numbers to get the desired oil clearance instead of re-measuring and so on.

graded bearings are only useful if using a BRAND NEW CRANK, then you can pick a grade to suit the size oil clearance you want. as far as im aware once the crank is linished all that goes out the window. (the grade numbers on the crank)

subaru do the same thing but with pistons aswell. each block has individual cylinder grades.

[blue_vl_t]

Just trying to get my head around what you guys are on about.........

so 'graded' bearings can be STD size but be very slightly different in size to suit each journal?? would this mean they have a different measurement size to each other and you order the size you want???

I have heard of people buying like three sets of bearing and measuring them all, then matching bearings that fit 'best' to suit each journal, and this slight difference comes from manufacturing tolerances being a bit out.

[The Dan]

Just trying to get my head around what you guys are on about.........

so 'graded' bearings can be STD size but be very slightly different in size to suit each journal?? would this mean they have a different measurement size to each other and you order the size you want???

I have heard of people buying like three sets of bearing and measuring them all, then matching bearings that fit 'best' to suit each journal, and this slight difference comes from manufacturing tolerances being a bit out.

exactly

[T04GTR]

in the "standard" journal size there are a number of grades. because when the crank is ground its ground to a cirtain tollerance. not an exact size like you get when building up a new engine. ie: at nisan there isnt a guy standing next to the linisher with a mic checking it as it goes.

hope that helps.

[Bl4cK32]

not an exact size like you get when building up a new engine.

why some of us like to get things blueprinted when building a motor...running tighter tolerances instead of "in between X and Y should work fine"

[ZimNismoBoy]

In more ways then one my questions have been answered and i would like to say a big thankyou to you all for contributing to what i thought would be a small response.

So To answer some other questions other forum members have asked yes you can get different grades of bearings from NISSAN japan.

So meaning that on a std crank size or what we would assume is a standard crank size, there is say 6 journals for the conrods to sit on and 7 mains for where the crank is held in place by the block.

So now each journal at the Nissan factory has to be polised and cleaned nice and shiny so that there is a smooth surface for the crank to glide on if it were rough it would mean oil would get trapped and damaged and also get hot because it would not be easily moved by facilitation of the smooth surface of the bearing surface and crank surface (this is my understanding) and hence the linishing part comes in.

So never less before i bore you guys to death.

I was looking for a explaination as to why Acl doesnt make a graded bearing.

Though we have the likes of Nismo Nissan Oem and others as well that sell graded bearings.

The crank, that im going to be using is a new crank and so is the block.

But now comes the tricky part does this process of using graded bearings use only the crank stamp on the end weight to confirm the bearing grade ? or do i have to use the block as well.

Or is it so that the crank stamp is for the bearings on the conrods and the bearings to be used on the crank mains are graded using the block stamp ?

Very confusing i think i should look at the rb26dett rebuild manual to confirm .

So never the less it is better to use a graded bearing, on the rather larger size if the engine is going to be reving quite hard and high then to use a standard across the board one bearing fits all (STD) cranks ???

And hence i come to the assumption that standard bearings are for when you have a regraded crank that is still close to standard and you would put std acl race or acl duraglide bearings in this type of application?

Maybe im wrong and in a way this a question to settle all the questions that have been asked in the past and present on the forum.

In a few months im going to be ordering a brand new crank shaft, and brand new block and will need to order a graded set of bearings to suit.

thankyou again for your time and patience and input some superb answers

[r31 25t]

From memory, for the crank, there are two sets of stamped grading numbers. . .

From front on it looks something like this. . . .

112211 <- (Ignore numbers they're just for example, But note there are six of them. These are for the rod journals.)

2211111 <- (again, example numbers, But note there are seven of them. These are for the main journals.)

On the block where the sump bolts to, there is also grading numbers. These are for the main tunnel sizes.

When selecting graded bearings for the mains or big ends you need to use the "look up tables" in the factory engine manual. If you are using non graded bearings you will normally have the crank and sometimes block machined to suit bearings and/or set desired oil clearance.

This is all from memory, so there may be errors. (been a while since I've slapped an engine together).

[StevenCJR31]

If your concerned about bearing clearences being incorrect may i suggest getting the new crank ground to the nearest oversize and buying acl bearings to suit?

[Adriano]

And lose the factory nitriding, no thanks. If it were my new motor, i would either get the correct nissan graded bearings, or the acl race and just check them. Why the new crank/block?

Edited July 11, 2011 by Adriano

[The Dan]

In more ways then one my questions have been answered and i would like to say a big thankyou to you all for contributing to what i thought would be a small response.

So To answer some other questions other forum members have asked yes you can get different grades of bearings from NISSAN japan.

So meaning that on a std crank size or what we would assume is a standard crank size, there is say 6 journals for the conrods to sit on and 7 mains for where the crank is held in place by the block.

So now each journal at the Nissan factory has to be polised and cleaned nice and shiny so that there is a smooth surface for the crank to glide on if it were rough it would mean oil would get trapped and damaged and also get hot because it would not be easily moved by facilitation of the smooth surface of the bearing surface and crank surface (this is my understanding) and hence the linishing part comes in.

So never less before i bore you guys to death.

I was looking for a explaination as to why Acl doesnt make a graded bearing.

Though we have the likes of Nismo Nissan Oem and others as well that sell graded bearings.

The crank, that im going to be using is a new crank and so is the block.

But now comes the tricky part does this process of using graded bearings use only the crank stamp on the end weight to confirm the bearing grade ? or do i have to use the block as well.

Or is it so that the crank stamp is for the bearings on the conrods and the bearings to be used on the crank mains are graded using the block stamp ?

Very confusing i think i should look at the rb26dett rebuild manual to confirm .

So never the less it is better to use a graded bearing, on the rather larger size if the engine is going to be reving quite hard and high then to use a standard across the board one bearing fits all (STD) cranks ???

And hence i come to the assumption that standard bearings are for when you have a regraded crank that is still close to standard and you would put std acl race or acl duraglide bearings in this type of application?

Maybe im wrong and in a way this a question to settle all the questions that have been asked in the past and present on the forum.

In a few months im going to be ordering a brand new crank shaft, and brand new block and will need to order a graded set of bearings to suit.

thankyou again for your time and patience and input some superb answers

Mate, you are thinking about this waaaaaay too much.

Get the ACL race series bearings and measure/assemble with those.

Even if you buy graded bearings you'd be an idiot to just screw it all together without properly measuring everything.

The ACL race series bearings are a tri-metal bearing, whereas, the Nissan bearings are a bi-metal bearing. The tri-metal bearings withstand something like 40% more load than bi-metal bearings.

We use ACl race series in all our engines and they are great. Just make sure you build it correctly or get someone who knows what they are doing to do it for you

[The Dan]

If your concerned about bearing clearences being incorrect may i suggest getting the new crank ground to the nearest oversize and buying acl bearings to suit?

That is the absolute LAST thing anyone should ever do.....ever.....ever

[ZimNismoBoy]

ok fair enough point taken, i am going to buy a standard size set of mains and big end acl bearings baring in mind that the crank and block are new it should be with in spec. but before i get shouted at lol im going to make sure i mic each journal and also check each block journal and also plastigauge it to make sure its all correct.

check twice assemble once .

Now i need to get one other factor checked the acl series race bearings have a X range is this for more clearance ?

or is this a smaller bearing ?

thankyou for the info ?

off topic but on engine assembly do i really need to use a dummy head torque plate to hone bores if it has already been factory bored on a new block ? like what tomei does, or should i assemble the motor as is ?

[ZimNismoBoy]

sorry forgot to mention, i need a new block because im fussy as hec, my old block went through a beating and was damaged it might need a line bore and the bores are slightly damaged needed bad honing and now the size is like 86.8mm i think if memory serves me correct.

Also because im rebuilding i want to use a fresh block, rods and pistons and new rings and bearings and new oil sprayers the old oil sprayers have bits of block stuck in them because the flywheel was dual mass and not balanced it wore the bearings so badly it walked and the counter weights ate up the block facing not enough to damage the bearing seats on the main journals but im still not happy .

same with the head was also damaged on the cam journals so i bought a new head because the cost of line boring the head cam journals was almost the same cost as a bare new head

[Bl4cK32]

by the sounds of it, your better off getting the machinist to do all the work, and give you back the lot ready for assembly. Its not worth attempting to save money on a hone when its worth like $80, and easy to stuff up.

[The Dan]

Piston to bore clearance needs to be checked depending on the pistons you are using.

I wouldn't just assume the bores are correct for your pistons.

[StevenCJR31]

That is the absolute LAST thing anyone should ever do.....ever.....ever

Why not? surely there must be a shitload of RB engines out there that are running reground cranks?

[JonnoHR31]

the cranks are nitrided from the factory. if you grind them you lose the layer of hardening on the outisde. sure it might work but it'll never be any where near as good as standard.

[Duncan]

really? how deep is the nitriding, and how much is ground off for oversize bearings?