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Hey,

Im a 4th year fitter and turner apprentice, so Ive got a bit of mechanical knowledge. But I have never had anything to do with internals of motors.. Ive been googling, sau'ing and wikapedia'ing a bit now, and ive just stripped down my doner rb25, and I've gained a bit of understanding about how everything goes together now. Just some quick questions on bearings though.

1. Im going to use ACL bearings and I'm just wondering about the calico coated ones. Is that the type everyone uses? Are they good for a street car or are they short term high performance bearings. (motor will be peaking out turbo at around 330rwkw, on a mostly street drivin car, some track work)

2. When you guys build your motors do you use plastigauge to measure bearing tolerances in the big ends and main bearings?

3. Does anyone know what the tolerance is on the bearings, and do the bearings come with all info on specs with them from new?

4. How do you guys check the thrust? With dial indicator on the end of crank and just tap with soft hammer on other end? or is a wiggle and a push all is needed to move crank?

5. When torquing down big ends, I think the ARP studs recommend 108.5NM (DONT TAKE THIS AS 100% CORRECT) If its torqued to that setting, and I check the bearing clearance and its too small.. what can be done? Linish inside of bearing?

6. Has anyone had to lap the thrust bearings to adjust the end float? Or should it fit straight in? What kind of end float should I aim for?

any help will be greatly appreciated.

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1. You want to use acl race series bearings. Its pretty much the standard that everyone uses. Common as.

2. Some people use plastigauge, some use micrometers and some use both. For your build plastigauge will more then likely suffice. Though as you are a fitter n turner, you should be competent with a mic.

3. What tolerance do you mean? The bearings dont come with anything spec wise. Just bearings wrapped in plastic in a small box. I think their specs can be found on the acl website though.

4. Dial indicator on the crank snout and you just push the crank forward and pull back by hand, it should be free. I dont know about others, but I usually make sure its 4-5 thou.

5. You dont touch the bearings. You usually linish or grind the crank journal, however acl do make 1 thou oversize bearings.

6. On the standard main girdle ive found that with acl bearings ive gotten the 4-5 thou without ever needing to glass them. But if so, a piece of thick flat glass, some wet n dry 600 i usually use cause thats all thats in the shed and some kero and do some figure 8's on both sides, usually an even amount and then clean and refit and check and go forward and back until you achieve your desired thrust clearance.

You should try and find the r33 service manual, it will have all the info you need and is handy to keep on your comp.

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Sorry should have explained number 3 a bit better. Just asking about the clearance I should be aiming for in mains and big ends. Is it 0.001" or 0.002"??

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There are a number of users here that can help you. Here is some information that Cubes gave me, and what he runs. (Rb30 in a R32, still going very well)

Sorry about the "scratchy" format but you'll get his jist. Just remember, his settings are tested and going well.

hey a few tips with the rb30 build

larger bearing clearances

Mains 2.5thou

Bigends that depends on rods a little but generally

2.2thou for up to 300rwkw; 2.5thou for 400rwkw+

the nissans from factory are setup quite tight so then need to be loosened up a little for the higher power levels

radius oil galleries where oil flows to from and down etc

drill the main oil galleries leading to the main bearings out with a 7mm long shank drill bit

match the bearing oil hole to the blocks oil feed hole

crank collar

thats all i can think of off the top of my head

N1 pump is good with the larger clearances providing you ensure you run a crank collar. the n1's are more britle and don't like the limiter

also go for an 8.5:1 if you remotely have intentions to run the gt35 and push 400rwkw

Edited by The Mafia

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Glad I could help.

One small problem though, Cubes doesn't go by that name anymore (well he didn't a while ago) I think he's got a new username now. He did mention it somewhere along the line but I have forgotten.

I have his number here somewhere too. If I find it I will let you know. Hopefully he shows up.

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hmmm interesting about the build details....wonder where he got that from...I didnt think anybody else did that.

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My engine builder did it. He said that you do need more loose clearances for higher power, but also higher oil pressure. I have shimmed my pump and raised the pressure a little.

Its really just what is working with everyone out there I guess.

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Yeh. its almost identical to how I build our rb30's. Ive mentioned it to others before and they didnt think it was right...

Anyway its good to see others doing the same thing.

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Yeh you really need a higher flowing oil pump. Not sure if the standard pump will flow enough. Though I guess if you keep revs to around standardish it wont be too bad.

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Thanks for the help. R33 racer, can you please tell me what clearances you would use if I'm aiming for 330kw ATM, but definately not ruling out going higher with a bigger turbo when funds allow for it. Don't think I'd go for more than 400kw though.

If you dnt want to post it please pm me. I'm also after end float of crank shaft.. Anyone else have more to comment on the float I should aim for?

And when you say bigger clearances, more pressure... How much pressure would you aim for? Nitto pumps have 120psi, that's almost double standard isn't it? What pressure are most of you guys getting from standard rb26 pumps?

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Go for the nitto pump!!! :D

I think the rb25 pump actually flows abit more then the rb26 pump or maybe it has slightly higher pressure. I think i saw the pump figures in the r33 service manual. Im guessing due to the hydraulic lifters...

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I shimmed mine - DaleFZ1 shimmed his also but a bit more for more pressure. He had a few issues with oil pushing past seals, but I think a lighter weight oil than the running in oil will fix that.

Are the RB25 pumps higher flowing? I thought the 26 was, but then again, I am forgetting that the RB25 possibly needs more oil due to hydraulic lifters, and the VCT.

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yes and the vct...forgot that bit too.

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Very informative thread as my bits are about to go to the machinist (as soon as I check clearances), thanks guys :P

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I'd aim for .003"-.004" (.075-.1mm). You can sand the thrust face of the bearings to set what you need.

Quote greg from proengines

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