Mikester

Below is a quote from a builder/fabricator named Rutger in the Netherlands whose skill, knowledge and expertise I have immense respect for. Not trying to sway anyone either way... but I am a firm believer in gathering as much info as I can before making parts choices so I thought I would share this with everyone:

"I've noticed people tend to think ACL bearings are some sort of gift to your engine and add to the spec list. I've so far found out the exact opposite. When I had a vg30dett rebuild few years back the shop supplied with me with stock fit ACL bearings. Plastigaged them, way to loose (like 1,5 times the stock maximum clearance). When I rebuild my brother's sr20det, I received ACL race bearings as the normal type had run out. Their clearance was 0.08mm vs 0.02mm max according to the FSM. That crank had the 'thickest' Nissan indexing and was not worn or ground down. When the 'normal' ACL type showed up, they were 0.055mm, again way to much. I eventually ordered the bearings from another manufacturer and they cleared correctly.

Now this may all seem like a coincidence to me till I ripped my old ca18det apart last week. That engine ran for 18.000km after a rebuild (with ACL main bearings) but was eventually removed cause I started on the vg30 project. The only thing wrong with that engine was oil consumption (replacing the piston rings wasn't enough at the rebuild), about 1 liter per 1000km and a slight lifter tap but it ran fine and was always filled up with full synthetic oil.
When I took the crank out, all bearings were worn to the metal on several spots. If the main ends are too loose the big ends get less oil pressure as well. I did not check the clearance on these bearings upon assembly and trusted the advice of the shop who told me these were the right bearings for an unmodified crank. None of the other oil-lubricated parts on that engine showed any wear. Pretty odd how just the crank and big end bearings were badly worn huh?

I don't believe in race bearings, and have never heard an expert say they exist. The bearing is just a part of the assembly. It's the oil that gets in between that does the work.I know true racing rods are often 'oval' shaped at the big end to allow the rod to pull the sides of the big ends together at extreme rpm's. By using more clearance at the sides, the bearings won't touch the crank. Has dick to do with the bearing in between.
The bearings are the stock fitment according to the word on the ACL box. Nissan works with thousands of mm's for it's grades, but the difference between the smallest and largest is often just 0.02mm. Therefore, most aftermarket bearing manufacturers use just 1 replacement size that's an average of the Nissan clearances (apart from undersized bearings for ground cranks). Tell me how it's possible that 2 sets of ACL bearings have abnormal clearance when another set from a different manufacturer clears like it should.
A bearing with 4 times the FSM maximum clearance kills an engine faster than an old bearing that's just worn over the minimum thickness. Be smart, always check the clearances on your engine when rebuilding. And don't believe that 'race' logo on that bearing's box. I will NEVER EVER buy ACL crank bearings again. Total waste of money"


Rutger

+++++++++++++++++++++++++++++++++++++++++

Food for thought...

--Mike

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greatwhitebuffalo

Good to know.

jr_ss

But, but, but, it costs more money...

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Kingtal0n

Just use 90W gear oil. problem solved.

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Gar9854

Calico coated OEM bearings ftw

Croustibat

ACL "tri metal" race bearings (and others) always make me laugh. Oem ones already are tri metal. The difference is ACL only has standard and reground clearances, like most if not all alternatives to nissan, whereas nissan has 4 sizes for standard and i think as many for reground.

The question is : do you need that exact clearance ? If so, go for nissans. If not, pick whichever you want.

Bearings are not black magic anyway.

Mikester

So... In other words, in a car that will see daily driving as well as track duty, exact tolerances would be best... and for say, a drag car that makes big power for short stints, and undergoes frequent teardowns/rebuilds; maybe the tolerances wouldn't be so critical. Is that correct?

Obviously, I am far from an expert on such matters- which is why I rely heavily on the few people that I absolutely trust... and also why I thought this may be something interesting for others in the same category.

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PoorMans180SX

Depends on the manufacturer. Some engines come standard with aluminum bearings that like to soak up gunk better than a tri-metal bearing. This can be good and bad. Clevite makes a lot of this type of bearing.

I agree bearings are not black magic.

Not really. Clearances are always important. It's important to match your clearances with what the car will be doing and what materials are in your engine. An aluminum rod engine is going to have different clearances than a steel rod one, and a drag racing, big power engine is going to have different clearances than a street one of the same build. They also change based on what your oiling system can handle.

Here at Force, we use ACL race bearings in all of our 6-bolt 4G63's, and they always mic out great (no we don't measure clearance with plasti-gauge, that's a joke). We use Clevite H or P bearings is most of our other builds.

But like it says in the original article, clearances are MUCH more important than what the bearing is made out of. Another often overlooked measurement is rod side clearance.

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Croustibat

I did not explain myself correctly:

Basically, if you are running your engine at high/ very high rpms, you need very tight clearances. but you need them everywhere: rod and crank bearings, rings, bore to piston and so on. It will also require a lot of maintenance, because these clearances must be kept tight.

If you are not trying to get the maximum power an engine can do, you can use looser clearances. Not saying that you should, but as long as you are in the manufacturer recommanded clearance, its ok.

Now there is another reason that you dont need to use nissans bearing: if another manufacturer bearing gives you exactly the clearance you need.


If you know your engine has never been reground, then you can use nissans marks on the engine block, crank and rods to get the correct part number. If you dont know, plastigauge is your new best friend.

PoorMans180SX

I would politely disagree. I'd say clearances have far more to do with piston and connecting rod material, power level, and oil pump capability.

Running tight clearances will be absolutely disastrous if the oil pump can't handle pushing the correct weight oil into those passages at high-rpm. Too much power with too tight of clearances will beat up the rod bearings pretty badly.

Opening up the clearances requires higher weight oil, but can provide more of a cushion of oil film, and can allow the pump to flow more volume vs having a higher pressure.

Moving to a dry sump usually solves a lot of oiling issues and allows tighter clearances or more power to be made.

Also, our aluminum rod 4G63 engines run much larger clearances than their steel rod counterparts, but we rev them to 10,000rpm. This is due to aluminum's higher expansion.

Also, plastigauge is quite inaccurate. It's far better to mic everything.

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Kingtal0n

LOL have you ever even built an engine? Not that it matters I guess, anyone can build an engine.

Sorry but there are many good reasons why using loose or tight clearances for high or low rpm applications exists. There is no one size fits all solution

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Mikester

Please don't turn this thread into a another urination contest. There are ways of communicating different methods & techniques that may be helpful to others without being disrespectful... thanks.

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Kingtal0n

I apologize. if somebody has built 5-50~ engines of different kinds and blown every single one of them up and discovered why they blew up they should post up. Otherwise, its just internet £eet talk.

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boyou2

from my 'knowledge', and I don't have a lot lol, clearances depends of the application of the engine (street, circuit, hard drag), BUT, the more harder/powerful applications you want, the biggest clearances you need, because of the expansion of materials.

It's not useles to read which clearances you have to use by applications from Wiseco, CP Pistons, Mahle etc....

When you know this, you can then, use clearances you need, and I always use measurement tools AND plastigauge, to confirm my measurements....

About ACL, I never understand WHY they sell 1 grade bearings where Nissan recommand 4 grades (for Nissan, I can't tell for other engine, but for Honda, it's the same, it"s recommanded to use OEM's)

Davidna2fi

...Food for thought... Tight on mains (.0005-.0009) and loose on rods (.0017-.0022) is what I have seen on Honda, Toyota, and other 4 cylinder engines that spin to 8K+ RPM from the factory. So explain this magical tighter on the rod journals for higher RPM? I've done some engine building and haven't had any oiling issues with tight on mains and loose on rods in that range of spec, also the most overlooked issue when I have been assembling engines is the block itself overheated severely and the main journal caps were extremely loose fitting, (took no effort to remove) and also the crankshaft is out of round which would cause main journal bearing failure and lower oil pressure to the rod bearing which would cause an engine to fail.

Def

Factory engines need tight mains to account for wear/scuffing of 200k+ miles of cold/semi-dry starts.

On a lower total mileage, but higher HP engine you want to open up the clearances slightly to make sure you get enough flow to always form the hydrodynamic bearing at higher RPM.

Tight bearings are much more likely to squeeze the oil film down in "heavy applications" just enough to "starve" the bearing of additional oil flow long enough to scuff it up badly (only takes a few microseconds).

This is not a case where more is better, but generally on the high side of OEM clearance, or even higher on some special cases is what's called for on a higher HP/lower total mileage build.

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sleepyS14se

this thread has alot of info thats conflicting..lol..

mikester, can you tell rutger to join this site and give some more info on this topic.

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95 S14 se RB25DET 348whp

Mikester

Rutger knows full well this site exists. Why he does/does not join is not my concern

There is a lot of conflicting opinions... I posted this merely to give guys (like me) who don't understand the intricacies of these things something to think about before going out & buying ACL Race bearings thinking that they are 'better' because 'race' is in the verbiage and because a bunch of dogmatic zilvians 'said so'.

Up above, some of these guys build high-revving powerhouses; while others build to OEM spec, while others build stuff in between- hence differences of opinion... and rightly so. It all boils down to experience & preference based on performance characteristics & goals.

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sleepyS14se

so do you think it would be safe to say that nissan oem bearing should be used regardless? i would like to know more on this subject and i believe it would benefit us if some engine builders could chime in. If this fellow rutger could join and get on here and explain that would be great lol..

I build engines but have never built a high performance nissan engine. I am new to nissans and being this is my first 240 i chose to replace the stock engine with another ka24de and did the 5 spd swap at the same time, well i am extremely disappointed in it's power so i am buidling myself a sbc 350, I will be using KING engine bearings because they are proven (in use of old ass chevys and what not and i always have great consistency with clearance)

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95 S14 se RB25DET 348whp

jr_ss

A lot of engine builders use Honda bearings in all their motors. I personally would use the Nissan/Tomei bearings and size them accordingly. I plan to have my next engine with all OE bearings. It's about 5-700 dollars it just bearings.

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sleepyS14se

honda bearings fit other engines besides hondas?? I have built handfuls of honda engines and always have used oem bearings but i am unaware of these honda OE bearing fitting other engines.. can you name some engines that can use the oe honda bearings?

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95 S14 se RB25DET 348whp

jr_ss

Nissan, Toyota and American V8 engine builders have been known to use Honda bearings quite frequently...

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S14DB

Nextel Cup Was the big one now it's filtering down to circle track even. Shrink the Rod journal to the 1.888 Honda size to slow down bearing speed.

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Comments should be taken as Opinions not as Statements of Fact

Mikester

@SleepyS14se...

I purposely did not post my opinion in this thread with respect to my personal choice(s)... Wanted this thread to start as an unbiased conversation topic where the folks who DO know these things can further the discussion for the benefit of all. To reiterate... Unlike you, I am not familiar enough with the inner workings of ANY motor to speak competently on this subject. My particular choice of internals is in my build thread; and in random recommendations in the tech threads. Rutger and a very select few others are the ones whose expertise I rely upon to steer me in the right direction. If you'd like to converse with Rutger, open an account at www.zeroyon.com. That's the forum started/owned/operated by the American guys who live(d) in Japan & learned these cars at the source. Immense amount of knowledge there.

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shogun!

The bearings must be strong enough not to flex or deform when the dynamic stress work on them. They have to keep their shape during extreme loads and temperature changes.
The oilfilm between the rotating part and the bearing transfer the forces from piston/rod/crankshaft to the bearing. The more power in the engine, the stronger and accurate the bearings must be. They are not alowed to deform.

These sites explains it all in a good and easy to understand way.

Hydrodynamic Bearings, by EPI Inc.

http://www.mae.ncsu.edu/eischen/cour...ringDesign.pdf

I would not judge a bearing producer if a store did not supply the correct size of bearings to a certain engine. I would double check the dimensions of the engine parts and get the correct size bearings according to that.

I have built enough of high powered engines to know the needs and demands.
In my latest very powerful ca18det I use ACL and they are spot on.

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sleepyS14se

PM sent to you sirrr

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95 S14 se RB25DET 348whp

Mikester

^^LOL are you sure? Don't see one in my inbox...

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sleepyS14se

i cant get on that site. it says i need to validate myself and enter a code but it says htm something 404 error. idk.

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95 S14 se RB25DET 348whp

Drift_FX

haas anyone mentioned these yet?

these make a huge difference for high reving motors.... the oil supply to the rod bearing is greatly increased...
(to my knowledge these are only for sr20 motors)

Gumbrick

Those are gtir bearings, Found stock on the gtir fwd SR. You need to machine, "Groove" your main journals to benefit from this bearing. They look to be Calico coated as well, which IMO is one of the best things you could do for a bearing. Coatings/ dry film lubricants are what sold me when I built my engine. they are highly effective in reducing friction, heat, and surface galling. Added benefits is the coatings loading/pressure limits and the ability to retain oil much better than a un-coated bearing...

As far as bearing clearance goes, it's all dependent on power goals. Hell, when I opened up my motor to build it, I was curious to what clearances were after it been beat on at 21lbs, 300hp for 3 years. The oem bearings had worn to .0016-.0020 anyway and I was still making great oil pressure( granted, the motors questionable previous life)... far from .0002-.0009 oem range...

I built my motor A tad on the loose side, .0022-.0025 mains, .0025 rods. Again, 430-450hp goals

They are loose ONLY because I intended to use a coated bearing. My tuner put together a sr a while back and wanted to experiment with "clearance vs. longevity" on a coated bearing and ran WILD loose clearance (35 rod and 30 main)That setup was still running great 4 years later, 450 rwhp... my opinion, I wouldn't go past 20 on main and 25 rod on un-coated bearings that wanted longevity


I think there is quite an advantage running the coating, not only on bearings and piston skirts,(dry film) but also thermal barrier crown coating on the piston tops.

P.S. Get yourselves some mit mic's