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      05-21-2022, 11:03 AM   #1
lforter
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N55 rod bearings recommendation

Hello, I want to remplace my rod bearings, wanted know what's good and what to stay away from, was considering King but I have seen some fail (vehicular DIY), was looking for ACL but there out of stock everywhere. Now there other brand, Kolbenshmidt how good are they?
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      05-22-2022, 12:07 PM   #2
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Quote:
Originally Posted by lforter View Post
Hello, I want to remplace my rod bearings, wanted know what's good and what to stay away from, was considering King but I have seen some fail (vehicular DIY), was looking for ACL but there out of stock everywhere. Now there other brand, Kolbenshmidt how good are they?
It comes down to one thing. One test is worth 1000 opinions. Unfortunately with the internet one opinion on a site that is well viewed can skew others' good results. While vehicular DIY had bad luck with the King bearings, I don't recall anybody having bad luck with them, fatty and myself among them.

I went with them for the additional clearance, as do many hot rodders. My logic is if there is a momentary loss of pressure there is a tad more lubrication in there to hopefully buy time until pressure is restored. Right or wrong I beat on my Pure 2 port injected N55 every time I drive it. Obviously after a proper warm up. Whatever your choice, please let us know how the install went, and do plastigage every bearing during installation.
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      05-22-2022, 06:00 PM   #3
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Plus 1 on what ozzie said.

Is there a reason you don't just replace them with oem rod bearings?
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      05-22-2022, 06:06 PM   #4
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I'll probably do them preventatively with oem bearings around 100k just for peice mind. Or whenever my oil pan starts leaking. With x-drive, getting in there will be a pain, so the way I see it may as well swap the while it's opened up.

I'm not diligent about letting it fully warm up before going WOT, so I'll definatly post how they look when the time comes. Knock on wood, hopefully I don't regret my relative disregard for proper warm up, and it will be a preventative replacement (as planned) when the time comes.
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      05-23-2022, 10:27 AM   #5
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King, ACL, OEM, Kolbenschmidt will all be just fine. It's usually recommended to use OEM bolts I believe.

Kolbenschmidt used to be an OE manufacturer for e30s and some other models.

I have coated King bearings because it's what the shop who did mine recommended. I've had no issues.

Vehicular DIY is the only person I've ever heard of having issues but I don't think his King bearings were defective. There are a few other more plausible explanations.

1) 220k mile engine had worn main bearings and the mismatch caused it
2) there was more timing chain guide material that was not cleaned out of the engine
3) he admittedly didn't let it warm up, so while doing this once shouldn't spin a bearing, it definitely could contribute if something wasn't quite right already
4) possible contamination while doing the job
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      05-23-2022, 12:28 PM   #6
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Quote:
Originally Posted by wheela View Post
I'll probably do them preventatively with oem bearings around 100k just for peice mind. Or whenever my oil pan starts leaking. With x-drive, getting in there will be a pain, so the way I see it may as well swap the while it's opened up.

I'm not diligent about letting it fully warm up before going WOT, so I'll definatly post how they look when the time comes. Knock on wood, hopefully I don't regret my relative disregard for proper warm up, and it will be a preventative replacement (as planned) when the time comes.
Why would you not let your oil fully warm before going WOT, especially on an engine with known rod bearing issues? Not really understanding that at all.
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      05-23-2022, 04:49 PM   #7
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Why would you not let your oil fully warm before going WOT, especially on an engine with known rod bearing issues? Not really understanding that at all.
Well, maybe they're not good reasons, but there are a few reasons why I do. Please keep in mind this is my own conjecture based off of my unique experience and thoughts, no testing to back any of it up, and certainly NOT a recommendation for anybody to not let their motor warm up before beating on it!!!

-from my readings, the rod bearing issue anecdotally seems related to oil starvation. In particular, long, high-g, left hand turns combined with the angle of the block starving the oil pickup. This scenario isn't happening on my commute.

-short commute. No point in daily driving a fast car if I can't get on it.

-Yes, oil viscosity changes with temperature. But in a previous job, I supported production of high viscosity solutions, and have done a lot of viscosity testing. Barring really cold temperatures (sub freezing), the difference in viscosty numbers you see at say 60F and at operating temp of 240F looks very significant. But in reality, I think the practical difference in terms of flowability and lubricity between those viscosities probably aren't that significant.

-colder, high viscosity oil doesn't flow as fast through the pump at a given pressure as it does when warmer, but that colder oil is also going to resist getting pushed out of the bearing gap more than when it's warm. So you probably don't need as much flow for the same protection when it's cold.

-BMW doesn't say let it warm up before beating on it. (But they also say not to replace your transmission fluid so probably not with putting stock in).

Again, no evidence for ANY of this, and NOT a recommendation to beat on a cold engine. Just the reasons I don't loose sleep over it. Hopefully I won't regret it.
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      05-24-2022, 04:50 PM   #8
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Quote:
Originally Posted by Ozzie335i View Post
It comes down to one thing. One test is worth 1000 opinions. Unfortunately with the internet one opinion on a site that is well viewed can skew others' good results. While vehicular DIY had bad luck with the King bearings, I don't recall anybody having bad luck with them, fatty and myself among them.

I went with them for the additional clearance, as do many hot rodders. My logic is if there is a momentary loss of pressure there is a tad more lubrication in there to hopefully buy time until pressure is restored. Right or wrong I beat on my Pure 2 port injected N55 every time I drive it. Obviously after a proper warm up. Whatever your choice, please let us know how the install went, and do plastigage every bearing during installation.
King bearings don't have "extra clearance" unless they are the "x" bearings.

Vdiy didn't really have any issue with king bearings. He put in aftermarket bearings and they spun a few months later... because spun bearings generally has very little to do with the bearing itself failing. Could've been poor stack buildup in the tolerance reducing crush or messing with some other key clearance but im confident whatever caused his spun bearings a few thousand miles after installing the KING would've happened no matter what brand he was running. Maybe he didn't torque rod bolts right. Maybe the rod caps were stretched. Maybe his car had a mechanical issue like misfires. who knows.
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      05-24-2022, 07:00 PM   #9
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at least 20k miles on my coated kings with no issues. I've been hard and beat on it a few times before it was over 160* also
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      05-24-2022, 07:02 PM   #10
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Will order calico coated king rod bearings, been looking for ACL for too long. Will report my findings
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      05-24-2022, 09:55 PM   #11
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Does replacing the rod bearings reduce any tapping sounds that you might have had, but weren't identified as a failed rod bearing?
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      05-26-2022, 08:27 AM   #12
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"King bearings don't have "extra clearance" unless they are the "x" bearings."

While I didn't specifically order X bearings, extra clearance is what I wanted and ended up with. Maybe they sent the X one anyhow.

As far as the diy guy, he had installed the King bearings, and made it a point to say so.
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      05-26-2022, 07:24 PM   #13
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Quote:
Originally Posted by Ozzie335i View Post
"King bearings don't have "extra clearance" unless they are the "x" bearings."

While I didn't specifically order X bearings, extra clearance is what I wanted and ended up with. Maybe they sent the X one anyhow.

As far as the diy guy, he had installed the King bearings, and made it a point to say so.
you ended up with ~.0025-.0027" clearance with king?
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      05-28-2022, 06:42 PM   #14
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Quote:
Originally Posted by bbnks2 View Post
you ended up with ~.0025-.0027" clearance with king?
I don't recall the exact numbers as it's been 3 years. But I discussed it with the sales guy, and my mechanic confirmed a slight increase in clearance with the spaghetti. As I am an old codger no longer making 6 figures, this is my end of life street rod, and hope my choices were right. Maintenance mode, and crossing fingers on bearing health is an OK place to be.
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