OEM vs ACL bearings


Going by that theory acl's should be fine to replace greens Browns blacks and blues

Could be a bit risky using them to replace yellows pinks or reds
 
On a relatively stock power engine that sees mainly road duty....
I think we are getting a little above our heads here, obviously sweating the 4th decimal place isn't as important as I first thought, perhaps coming within 0.0005" of OEM clearance is satisfactory. Perhaps even favoured if it's wider clearance on a higher power, track based car like mine.
 
Yep I agree^
Another thing you have to remember is your not building this engine to do 180000 miles and it's not going to be doing like 50000 cold starts either which is were most wear takes place due to the brief time with no oil pressure.

When they are building engines in the factory they have to factor all these things in.

When running on track your going to have around 80 psi of oil pressure between the crank and bearing most of the time
 
Yeah that's another good point.
I mean I won't do 25k in this car in 5 years.
 
It was a good while since I was checking these out but I was advised to just go OEM on bearings. IIRC it's the softer material used in the ACL race bearings makes them more susceptible to picking up debris and scoring a journal that is the issue.

But, as I said, it was a good few years ago I was looking at it now so I may have that wrong.
 
That's certainly another way to look at it that I hadn't thought of before.
 
Kozy said:
It was a good while since I was checking these out but I was advised to just go OEM on bearings. IIRC it's the softer material used in the ACL race bearings makes them more susceptible to picking up debris and scoring a journal that is the issue.

But, as I said, it was a good few years ago I was looking at it now so I may have that wrong.
Click to expand...

If you get big enough bits of debris in there your going to have that problem what ever bearings you use,

My thoughts in it are if the ACL are softer then smaller debris may get imbedded deeper and almost absorbed rather than just stuck in the surface scratching away at the journal.
 
Really interesting read! love this forum :D

unfortunately i'm measuring with pink big ends and brown mains so I'm going with OEM for piece of mind I was a little sceptical they were all the same so it's being triple checked by someone else at the machine shop. Kinda wish I'd done it myself now but I didnt have the tools or trust myself.

@Rybean I got a really good price from Tegiwa for OEM bearings :nice:
 
Got my mits on a service manual for a dc2
Maybe usefull to b16a my not be, but here's what I've found

Oem specs for b18c5(c6 here in the uk)
All in inches (service limit in brackets)

Piston to wall - .0004 - .0016 (.002)
Ring end gap(top) - .008 - .014 (.024)
Ring end gap(2nd) - .016 - .022 (.028)
Rod end play - .006 - .012 (.016)

Mains dia.(1,2,4,5) - 2.1644 - 2.1654
Mains dia.(3) - 2.1643 - 2.1653
Rod journal - 1.7707 - 1.7717

Main bearing.(1,2,4,5) - .0009 - .0017(.0020)
Main bearing.(3) - .0012 - .0019(.0024)
Rod bearing. - .0013 - .0020(.0024)

So quite a wide variance in clearance is with oem specs, even more so for service limits highlighted in (brackets)
This leads me to believe that the ACL, even though one size fits all, will fall into the oem specs on every journal unless real unlucky.
 
jesse888 said:
Got my mits on a service manual for a dc2
Maybe usefull to b16a my not be, but here's what I've found

Oem specs for b18c5(c6 here in the uk)
All in inches (service limit in brackets)

Piston to wall - .0004 - .0016 (.002)
Ring end gap(top) - .008 - .014 (.024)
Ring end gap(2nd) - .016 - .022 (.028)
Rod end play - .006 - .012 (.016)

Mains dia.(1,2,4,5) - 2.1644 - 2.1654
Mains dia.(3) - 2.1643 - 2.1653
Rod journal - 1.7707 - 1.7717

Main bearing.(1,2,4,5) - .0009 - .0017(.0020)
Main bearing.(3) - .0012 - .0019(.0024)
Rod bearing. - .0013 - .0020(.0024)

So quite a wide variance in clearance is with oem specs, even more so for service limits highlighted in (brackets)
This leads me to believe that the ACL, even though one size fits all, will fall into the oem specs on every journal unless real unlucky.
Click to expand...


The thing is you will probably check that your crank is with in spec (with a micrometer) then check your bearing clearance with a plastigauge!! , I would not worry about the clearance of the ACL's being that they will be to green spec, and how accurate is a pastigauge.
 
Yeah this is what I'm saying now. But didn't want to go buying ACL and then half of them be unusable because of clearance.
Plasti gauge is accurate but not perfect. I will use it but only to check my work with more accurate tools. This gives me two chances to find an issue should I get one.
 
jesse888 said:
Yeah this is what I'm saying now. But didn't want to go buying ACL and then half of them be unusable because of clearance.
Plasti gauge is accurate but not perfect. I will use it but only to check my work with more accurate tools. This gives me two chances to find an issue should I get one.
Click to expand...

I think people over think the process, to get a truly accurate measurement this would have to done under controlled conditions.
 
You know there are three sizes of ACL right?

Normal, plus a thou, minus a thou.

I'd be tempted to go halves on all three ;-)
 
There's plus sizes for ground cranks aswell,
Same still applies really.
I'll be measuring the clearances with ACL bearings on my crank next month so will post my exact findings, hopefully down to the 4 decimal place.
 
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