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Bearing and Clearance Recommendations

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31 replies to this topic

#1
parkermotorsport

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What are you guys using for bearings in the 800-1100 whp builds? OEM or something like the King race bearings?

I did talk to King and they were actually pretty honest in not necessarily recommending them for street builds due to the thinner top overlay that does not have much tolerance for wear before hitting the harder middle layer. Does anyone have any lifespan experience on the race bearings?

Any specific clearance recommendations other than stock? The specific markings for the parts for this engine are below. Oddly, the Nissan bearing chart shows main journal 1-4 on the top line of the crank markings but there are 5 characters in that line and 5 squares in their diagram... I'd imagine one would disregard the 4 in the example below.

Block main bores:
KMMP

Crank:
4MLNN
DHGHGD

Thanks!

#2
Bill@SiR

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I would recommend measuring the actual bering clearance. 

 

So put bearings in the block, torque the girdle down, measure the crank, zero the dial bore gauge in each crank journal, and measure the clearance (difference after zeroing) in the block.  

 

No guess work, no math, and your measuring the actual clearance.  

 

You are dealing with crank tolerance, block tolerance and bearing tolerance.  To me it makes no sense to guess.  



#3
Doug@WGP

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This Parker guy loves to ask the questions where the answers make the rest of us a living

Doug Ross
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#4
parkermotorsport

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Thanks for the info Bill. Maybe I'm giving too much credit to Nissan and their umpteen step grading process, perhaps it not that accurate after all.

Doug, you seem very protective but weren't you the same guy that used to post under the HighlanderD screen name before WGP and posted the engine removal and tear down steps? I recall it being a 'Christmas Present' to the community and was good info.
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#5
Doug@WGP

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Thanks for the info Bill. Maybe I'm giving too much credit to Nissan and their umpteen step grading process, perhaps it not that accurate after all.

Doug, you seem very protective but weren't you the same guy that used to post under the HighlanderD screen name before WGP and posted the engine removal and tear down steps? I recall it being a 'Christmas Present' to the community and was good info.

More importantly than offering the "answer" the bearing clearances vary depending on the setup and are specific to each builders preferences and goals.

Doug Ross
Owner of Weapons Grade Performance
-Northeast/Pacific Northwest Shops where we ONLY work on GT-Rs
-Owner/Builder of the 1st Ever Home Garage GT-R Drivetrain Removal
Cobb Protuner / EcuTek Tuner
-All Wheel Drive Mustang Dyno in House
doug@weaponsgradeperformance.com
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East Coast Location 226 N. Plains Industrial Rd, Wallingford CT 06492 203-668-4765


#6
tech@epr

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A lot goes into specifying an adequate oil clearance.  Its not just about cold clearance numbers but you have to take into account compression forces by cylinder pressures you expect the system to endure along with expansion scenarios that grow clearances as well.  I agree every engine should be setup based on the intended use and application of the engine itself.  There is no universal clearance for all applications.  I certainly wouldn't setup an engine for 600HP with the same oil clearance as one making 1500HP etc.  While each company/engine builder likes to run their own clearances its honestly not a "secret" of sorts.  It comes more down to experience in setting up the application and knowing from past builds etc where you want that cold figure to be.  Same applies for ring gaps. 

 

Im not a believer in graded bearings even though Nissan got their act together when they designed this VR platform, I prefer to use a quality race bearing that has better backing and better lead/tin/copper layers than what Nissan uses.  Factory bearings offer a degree of "cushion" in terms of embedding  of FOD / contaminants that is a little more forgiving in the event the owner lacks in maintenance etc.  All Nissan bearings are like this but were never really designed for a racing application of sorts.  This is the reason why we have fantastic companies like King that produce some of the best bearings on the market for an aftermarket sector.  I personally use KING bearings in all my engine builds and swear by them.  Every shop has their own rules to the exception or what they like to run etc. 

Biggest thing outside of what bearing clearances you plan to run is ensuring you have very concentric bores for all housings to include the mains/rods and cylinder bores.  Factory bores have a bit of taper at the bottom of the cylinders that can pose an issue with "pinching" of the bottom of the skirts.  This is common and can be easily resolved with the correct processes put into play. 

Good luck with your build!


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#7
V8killer

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Look at Clevite they make a great race bearing for mains and rods.

#8
parkermotorsport

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Thanks for taking the time to post, I appreciate the information!

A lot goes into specifying an adequate oil clearance. Its not just about cold clearance numbers but you have to take into account compression forces by cylinder pressures you expect the system to endure along with expansion scenarios that grow clearances as well. I agree every engine should be setup based on the intended use and application of the engine itself. There is no universal clearance for all applications. I certainly wouldn't setup an engine for 600HP with the same oil clearance as one making 1500HP etc. While each company/engine builder likes to run their own clearances its honestly not a "secret" of sorts. It comes more down to experience in setting up the application and knowing from past builds etc where you want that cold figure to be. Same applies for ring gaps.

Im not a believer in graded bearings even though Nissan got their act together when they designed this VR platform, I prefer to use a quality race bearing that has better backing and better lead/tin/copper layers than what Nissan uses. Factory bearings offer a degree of "cushion" in terms of embedding of FOD / contaminants that is a little more forgiving in the event the owner lacks in maintenance etc. All Nissan bearings are like this but were never really designed for a racing application of sorts. This is the reason why we have fantastic companies like King that produce some of the best bearings on the market for an aftermarket sector. I personally use KING bearings in all my engine builds and swear by them. Every shop has their own rules to the exception or what they like to run etc.

Biggest thing outside of what bearing clearances you plan to run is ensuring you have very concentric bores for all housings to include the mains/rods and cylinder bores. Factory bores have a bit of taper at the bottom of the cylinders that can pose an issue with "pinching" of the bottom of the skirts. This is common and can be easily resolved with the correct processes put into play.

Good luck with your build!



#9
parkermotorsport

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Not surprisingly, the new block and crank measured exactly as the stamps and FSM charts read. The curious part is, if one were to go off the bearing chart, that would only leave around .0006 to .0008 oil clearance after doing the math from the individual measurements.

For example:
Main bore "K" 2.7560
Crank main pin "M" 2.5576
Grade 3 bearing 0.0988-0.0989 (x2)

Equals only 0.0006 - 0.0008 clearance

This is only roughly half of the 0.0014 - 0.0018 factory spec. I wonder if the charts take into account what the operating temperature clearances will be as opposed to what the cold measurements calculate to out be? The manual doesn't mention this but otherwise I haven't come up with an explanation for the chart recommendations. Even using metric measurements to rule out conversion errors doesn't explain the discrepancy. Does anyone have any insight?

#10
Doug@WGP

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Why would you want to use the factory clearances on an engine making more than 2x the power? ;)


Doug Ross
Owner of Weapons Grade Performance
-Northeast/Pacific Northwest Shops where we ONLY work on GT-Rs
-Owner/Builder of the 1st Ever Home Garage GT-R Drivetrain Removal
Cobb Protuner / EcuTek Tuner
-All Wheel Drive Mustang Dyno in House
doug@weaponsgradeperformance.com
Our Online Store
East Coast Location 226 N. Plains Industrial Rd, Wallingford CT 06492 203-668-4765


#11
parkermotorsport

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Why would you want to use the factory clearances on an engine making more than 2x the power? ;)


I agree and am not saying that is the ultimate target, I'm just trying to understand how the engineers came up with the existing recommendations.

#12
HiBoost

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Not surprisingly, the new block and crank measured exactly as the stamps and FSM charts read. The curious part is, if one were to go off the bearing chart, that would only leave around .0006 to .0008 oil clearance after doing the math from the individual measurements.

For example:
Main bore "K" 2.7560
Crank main pin "M" 2.5576
Grade 3 bearing 0.0988-0.0989 (x2)

Equals only 0.0006 - 0.0008 clearance

This is only roughly half of the 0.0014 - 0.0018 factory spec. I wonder if the charts take into account what the operating temperature clearances will be as opposed to what the cold measurements calculate to out be? The manual doesn't mention this but otherwise I haven't come up with an explanation for the chart recommendations. Even using metric measurements to rule out conversion errors doesn't explain the discrepancy. Does anyone have any insight?


I agree the service manual numbers don't add up like you might hope. That said, I have always thought that the uninstalled bearing thickness is a bit of a "who cares" number. The only thing that really matters is the clearance and to really know that you need to install the bearings fully and measure that ID and then compare that to the OD of the crank. Trying to add the two shells and subtract from the block doesn't take into account any type of "crush" and therefore I can't see the usefulness. The only exception would be if I had already installed a set of bearings and they were, say, a bit too tight, then I could measure those bearings uninstalled and look for others that are slightly thinner also uninstalled. So to say "tighter or looser", sure, but to predict the final clearance number without actually installing them doesn't seem very likely.
-Jeff

#13
parkermotorsport

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Certainly, the diameter of the bore with the bearings installed is more important but you have to start with a baseline set of bearings to get the initial measurements, hence the shell thickness does factor in, at least to me. I suspect, like many that have gone before me, Grade 0 bearings will be what is required to achieve the actual desired clearances. I guess the engineer side of my brain is just curious of the thought process that was used to come up with the factory 'system'.

#14
HiBoost

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My point was, you should take your stock bearings and torque the caps down and measure them and I bet you'll see that you are in fact in spec when comparing that ID to your crank's OD to determine the true oil clearance. Your original post made it seem like you thought you might be out of spec. You also mentioned temperature as a potential reason but that's now how things are spec'd as there's no good way to achieve operating temperatures in the build room when doing the measurements. I still don't follow what you mean by needing a baseline and that being tied to the shell measurement. Get your baseline with the bearings installed, then go up or down in grades from there. What the bearings by themselves measure is irrelevant unless you are trying to source a bearing from some other application and need a starting point.
-Jeff

#15
parkermotorsport

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These are brand new components so there aren't stock bearings per say, I should have clarified that.

#16
HiBoost

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I'll give this one more shot, feeling like we just aren't communicating. New, old, whatever, if you want to know what the clearance is you need to install them in the caps and torque them down and take that measurement - or put the crank in too and use plastigauge. Your post indicated a "discrepancy" in your measurements and I'm arguing that there likely isn't a problem, you simply aren't doing the measurement properly.
-Jeff

#17
parkermotorsport

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I agree this feels like miscommunication. The measurements I posted above are straight from the factory charts for parts with those stampings but I did verify the charts do match the actual measurements taken on these parts so I feel the discrepancy lies in how the factory does the 'math' to arrive at their recommendations. That said, a good portion of this discussion is academic since I do plan to take my own actual installed clearance measurements as you and others have suggested. I do also have a previously used shortblock I'll probably do some experimenting on to help with my curiosity.

#18
HiBoost

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Dude.  There is no discrepancy.  There is no "math" in quotes to suggest something is fishy with Nissan or their engineers.  YOU ARE DOING IT WRONG.  Right here, from the service manual:  "Install main bearings to cylinder block...tighten to specified torque... measure inner diameter of the main bearing with a bore gauge..."

 

ss.jpg


-Jeff

#19
Cicio@TSM

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No offense but anyone that actually has this information and has proven it has taken risks or spent money to learn what these cars actually like, and l likely will not share it. 

 

 

It is one of those questions that if you have to ask it on a public forum and rely on enthusiast to be your information you probably shouldn't be doing it. 

 

 

Best of luck however.

 

 

Oh and Jeff is right... measure twice cut once :) 


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#20
parkermotorsport

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HiBoost, now we are getting somewhere! It all makes perfect sense now, the chart is just a starting point to choose an initial bearing set that you can take the actual measurements from, which is what I had planned to do in the first place before I got hung up on the methodology behind the charts. Lol




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