How to determine bearing size??

[C-unit]

I am currently in the state of rebuilding my SR20DET. I have some question regarding on the rod, big end and thrust bearing. How do I know what size I need to order? I've seen some engine builder putting a lil wax stick between the two surface where the bearing sits. Then they tighten the bolt with the correct torque and losen it after. There were a chart saying what size of bearings are needed from the width of the wax stick after it got compress. Does that chart included in the FSM?? Because from my local tunning shop that I was going to bring the engine in, they told me if you didn't sprung your bearings, you can just order the oem size. I got very confuse after that..
Also, What kind of bearing do you guys recommand:
Nismo
ACL
oem??
what else are there??

my set up are
Red top SR20DET
GT3076R
Exotic Speed 38mm wastegate
top mount manifold
Tomei 1.2mm HG
CP piston
eagle rods

[Sileighty_85]

Well you got the process of it down.
The FSM will show you how to do it
Although it kinda complicated if ya never did it before

What your shop is talking about is if your engine has a "Spun Bearing" When the bearing "spins" it makes contact with the crank shaft and starts fucking up the machined/polished surface of the Crank.

Alot of times the bearing will wedge themselves like this )) when the bearings should look like this () thats when shit really gets bad cuz then the crank makes contact with the Bearing Caps and starts grinding away.

So if your engine has a Spun Bearing you need to take it to a Machinest and have them grind and polish the crank if its reusable. Get it balanced while your at it. (Makes a big differnce in reducing Vibration in High RPMS)

ALot of these engine come from Americans that owned them over there, Majority of them are military and they buy the car for 2,000 bucks and dont take care of them, and beat the shit out of them drifting them cuz they will just sell it in 2 or 3 years. so they just dont care.

Go to www.RHDJapan.com (http://www.RHDJapan.com) they Have PE bearings, Nismo, Tomei
I used Nismo-Mains and Tomei- Con Rods

When I built mine, I used standard size bearings cuz my crank was still good, But when I installed the bearings I still Plasti Gauged the bearing clearance to make sure.

[Master Chief]

The piece of WAX you talk about is called PLASTIGAUGE, and it is used to determine clerance of bearings (amongs other).

On ROD bearings it is problematic to get a good result using PlasticGauge.
When the ROD MAIN cap is torqued in, with the PlasticGauge iserted into place, it is very important not to apply any force or disturb the PlasticGauge when removing the cap.
It is nearly imposible to remove the Rod CAP, especialy on the Ealgle Rods, without affecting the PlastiGauge reslut.

On the Main bearings, it works much better, as its much easyer to remove the cap, without affecting the PlastiGauge reslut.

Anyway, i recomad using a BORE gauge, and not PlasticGauge.
PlastiGauge is mainly good for use as a refference, only.

If you never used a bore gauge, i sugest finding a reputable machine shop, that knows what its doing, and let them do the work and select the bearings for you.

Know that the OEM crank jurnals are not always the same size, and hence need different thikness bearings to achive the needed clerances.
The Grades are stamped on the Crank, but i sugets measuring them anyway.
The variation could be more then 0.02mm between two jurnals, for example.

In general, you have two options - OEM bearings or after market bearings.

OEM bearings come in many grades (different thikness) - 3 STD grades are available for the ROD BIG ends, and about 7 Grades for the Mains.

Most aftermarket bearings come in only 1 grade.
You have Tomei and PowerEnterprise, that have bearings in simmilar grades to OEM for the RODS Mains, for example.

Anyway, dont get to paranoid about this.

You should do the following :

1) Decide for what power and usage do you intend to build the engine for.
2) Decide on the Clearances wanted for the Main and Rod bearings.
3) Ask the machine shop to inspect the crank and let you know what Bearing thiknesses you need to achive the desired clearances.
If the machine shop is able to have the crank dynamicly balanced, it might be better to have all the jurnals ground to a simmilar size for much easyer bearing sizing and consistency.

Remeber, the must important think is the bearing CLEARANCES, and not the brand. All the major brands you menchain are good, and you cant really go wrong - unless you mess up the clearances.

Personaly i have made a lot of research about this, and found many opinions, from MAZWORX to NORRIS-DESIGN, to many other builders....
Some run Thighter, some rune looser - depends.
For my engine - intended for about 500hp, i went for 0.0022" clearance for the RODS and about 0.0025" for the MAINS.

If you plan to go about 300HP, the OEM clerances in the FSM are a bit to tight, unless you go on the looser side of things.

I sugest you read the manual a bit more, bofer venturing into a rebuild.

Good luck !

[C-unit]

thanks for the suggestions, I'll keep doing more research on this. Regarding on the clearence, so the tighter it is, the longer it will last under heavy load?? Did I get it right or is it the totally opposite??

[RedtopTech]

Plastigauge is not accurate enough for modern engines that are built with tight clearances and high rpm use. It worked fine when all you needed to know was if you needed stock size or a step up.
With a visual inspection of the crank showing no signs of wear (a light scratch hear or there is to be expected) you can get away with using factory sized bearing's. On the sr the each rod could require one of four different sized bearing. Each main could be one of 5 sizes i believe. To determine the factory size for each journal, you take the numbers that are stamped on the block and the numbers that are stamped on the crank and add them together. Refer to the chart in the fsm for the bearing that corresponds to the sum on each journal. This procedure should be fine in most cases however if you want precise clearances (who doesnt?) the best procedure is to use a micrometer to measure the journal and then a bore gauge for caps (main caps installed/rod caps installed). The difference b/w these numbers minus your prefered clearance will give you the thickness of each bearing you need.
example: rod journal 1 measures 2.000 in.
rod big end measures 2.0050 in.
prefered clearance is .0020 in.
required bearing would be .0030 in. thick

[Master Chief]

"Regarding on the clearence, so the tighter it is, the longer it will last under heavy load?? "

NO !

The heavier the load, the more force is applied on the thin oil film the crank floats upon, and seperates the crank from actualy tuching the bearing.

Tighter clerances, mean that the oil film is thinner.... the thinner it is, for whatever reason (low oil pressure, tight clerances, etc...), the more chance for it to break, and let the crank tuch the bearing, under a certain amount of load - resulting in a spined bearing.

On the other hand, too loose clerances, reduce oil pressure, wich allso can cause the oil film not to be able to sustain the crank from tuching the bearings under havy loads.

So its kind of a trade off..... To tight and at high loads it can spin a bearing, to loose and oil pressure will drop too much and allso cause a spined bearing.

Allso looser clerances, mean it takes longer to build oil pressure at start up. Until the pressure is up, the crank is basicly tuching the bearing, wich will shorten bearing life.

There is allso a cooling issue to this, as if oil FLOW is affected, bearing cooling is affected as well. Oil pressure, will affect oil FLOW.....

Anyway, the best thing would be loose clerances, with a high flowing oil pump, but these are not easy to do on the SR.

On my setup, with my clerances, i should be ok for about 500HP, and the oil pressure was very little affected - i would say - hardly affected.

For 300HP, stick with the OEM clerances as i said, but go on the looser side of the range. Looser means allso less friction/heat - this a welcome benefit.

[rotation3x]

I want to put a crank from a different motor in my new motor and
use the rods that are in the new motor on the different crank.

How can I determine my bearing sizes?

I was told since it didn't spin a bearing I can just take the 5 digit number of the block and crank and add them together for my mains but for the rods I don't know what to do

so for my mains I would have
11232 block
21222 crank
32454 for my main bearing size

[xdumbxguyx]

those are right bearing sizes u need. rotation3x. always use plasticgauge to measure clearance to see if it is within spec.

[rotation3x]

Thanks! Should I use my old bearings with the platiguage to check the specs or buy the new ones then check and juggle them around to which ever is closest?

The machinest that polished my crank said I take the 5 digit number off the crank and order those size bearings for the mains. I tried telling him about the numbers on the block but yeah he made it clear he was right. Anyways I still need to figure out my rod bearing size. I wish someone in my area could help.