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Discussion Starter #1 (Edited)
I believe this is the undersized set for extra clearance. Consistent results thus far.

I'm repeating plastigage with red plastigage since the current readings are at the very end of the green plastigage spectrum, and I don't trust its window of accuracy at the very end of the scale.

This has been a learning process. There are a few things you need to know when doing plastigage upside down for the usual s85 rod bearing job fashion:

1. seat the upper shell on the journal completely before bolting up the bottom (removing plugs makes this easy)

2. never put the bottom bearing shell up against journal manually. just let it hang loose while finger tightening the rod bolts. You want the rod bolts to do all the pressing up, not your hand. pushing up against the bottom shell with your hand will give you artificially decreased clearance.

3. you need to do 2 rod bearings together at a time. if you do them individually, the rod will slide and twist against the journal while you're torque'ing it down and it'll smear the plastigage giving you artificially decreased clearance. having 2 rods in there limits this twisting and sliding significantly giving you much more consistent and real readings.

yes i know dial calipers are the gold standard. all i can say is, i think plastigage is much more prone to operator error for the above reasons. if dial caliper measurement doesn't fall within plastigage measurement window, you're doing it wrong.

moving on.

0.003 INCH is clearance i am getting with 1580HX-STD race bearing set. This will be confirmed with red plastigage next week.

what I don't know is, is that too much clearance for street driven s85? what if it's 0.004inch? It'll be supercharged if I can find it to my satisfaction that the clutch and smg will hold the power reliably.

Pics below. #1 cylinder isn't attached because as I said it's a learning process and in the beginning, I wasn't doing it correctly. The full set of pictures will be posted once I receive the red plastigage in mail.

I used ARP bolts and these were tightened to the recommended 50ft-lb.


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Is it just me or pics 8 and 10 look like a damaged crank? Just thinking out loud but your bearings may have been changed by PO as there was bearing damage. You could look at con rod caps to see if there's signs of a spun bearing.
 

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I just did a ACL bearing STD-HX series change with the .025mm. cearance

With the oem bearings got a .050mm and the ACL got a .075mm



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Also be aware, I just spoke to one of the engineers at ACL and asked him about the cleaning process and he strongly recommended not to use any brake cleaner or abrasive due to it will take off the top layer coating. Also another note there is no upper or lower shell with these bearings
 

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Discussion Starter #8
i didn't use any abrasives but i'm sure brake cleaner is perfectly fine as long as you have good bearing lube on it. i think it's only for break-in if i remember correctly?
 

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He said that the pre packing oil is no harm to the engine. But I asked this question because I notice using brake cleaner with a clean paper shop towel caused a few scratches in the top coating. He recommends using standard degreaser or engine oil.

He also said that there is no need for any run in procedure
 

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Discussion Starter #10
confirmed with red plastigage. nothing much to say really. these will give you clearance between 0.003 to 0.004".

i understand it's hard or even pointless to comment on bearing clearance consistency with plastigage, but the width of the plastigage was consistent with green-plastigage and little all over the place with the red-plastigage. i will add, i only torq'd the ARP to 30-40lb with red plastigage just because i felt that would be enough. maybe that was the issue. green plastigage pictures were all torq'd to 50ft-lbs accurately.

I did 6 of the 10 with red plastigage. didn't really feel the rest was necessary due to consistency with the green plastigage as before. I wanted to do red just to make sure i can trust the green results. and i do now. and given the result with red-plastigage and result posted by muckman, ACL HX race bearings seem to give us around (tiny bit over) 0.003" clearance.

waiting on a few things, so probably engine fire up next week/next wknd. i still have my vanos solenoid stuff to sort out, so it may be a little longer.
 

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Discussion Starter #13
just wanted to give you guys update on the ACL bearings.

I put about 300 miles since install. I have no issues with oil pressure, no issues with high rpm, no issues with running the crap out of the engine for hours. Did runs to 150mph multiple times. No issues.

It has even higher clearance than BE without all those problems. Will continue to update, but if I were to do this again, I would choose ACL over BE. and I don't give a crap about the $500 savings on rod bearing.

Only downside is that ACL doesn't come with separated bottom and top shells. That would be nice touch to keep the consistency tighter.
 

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After read countless RB threads, I think I will be going with ACL bearings as well from Lang Racing. What are you guys using for rod bolts? Are new OEM rod bolts ok to use with ACL?
 

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After read countless RB threads, I think I will be going with ACL bearings as well from Lang Racing. What are you guys using for rod bolts? Are new OEM rod bolts ok to use with ACL?
Right now mine are getting Lang Racing ACL bearings with BE ARP bolts. You can contact Andrew Lang at Lang Racing and he can explain any questions to you further.
 

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Are you guys concerned with distortion with stronger bolts (granted they are being torque accordingly?)

BE has an article about it and OE seems like they don't fail and can get properly torqued.


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Discussion Starter #18
going tighter clearance than what ACL offers you from factory make no sense to me. tight clearance --> RB flakes --> vanos problems --> empty wallet is the cycle of the s85. I went with full ACL set (p/n above). No issues with over 30k miles. It's my daily driver. No problems!

as for bolts, give me a break. you guys are overthinking this. it's a f'ing bolt. just get ARP if you plan on keeping it long time (so you can reuse them at next bearing change). get OEM if you are already getting sick of pouring gas in her every 200-250 miles or so!
 

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Discussion Starter #19
imo, you want to run bearing clearance based on our journal diameter and 60w oil. i think the clearance should be at least 0.003 if not toward 0.004. if you fight to keep it near where bmw had it from factory, you'll find yourself in an uphill battle to keep the car.

btw, i get the tendency to keep the clearance near how it left from the factory. obviously, bmw had spent lot of time and money to figure it out. however the history clearly has proven that they were wrong. JUST GET 10B1580HX-STD. ACL has way more experience in setting bearing clearance than anyone else claiming they know better for the S85. if you're in the camp that think spending more money will get you more quality when buying parts, pm me. I have lot of parts to sell you at a huge markup.
 

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imo, you want to run bearing clearance based on our journal diameter and 60w oil. i think the clearance should be at least 0.003 if not toward 0.004. if you fight to keep it near where bmw had it from factory, you'll find yourself in an uphill battle to keep the car.

btw, i get the tendency to keep the clearance near how it left from the factory. obviously, bmw had spent lot of time and money to figure it out. however the history clearly has proven that they were wrong. JUST GET 10B1580HX-STD. ACL has way more experience in setting bearing clearance than anyone else claiming they know better for the S85. if you're in the camp that think spending more money will get you more quality when buying parts, pm me. I have lot of parts to sell you at a huge markup.
So you are using the extra clearance ACL bearings with 10w-60 oil?

I plan on going with ACL for sure, 10B1580HX-STD is cheaper than Lang’s custom clearance ones, not that $100 makes or breaks anything doing this project. Just want to do it once and never worry about for another 50k at least.


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