Oversized crank bearings
 

Just got off the phone with my parts guy at the mazda dealership in town and he said he has a listing on over sized crank bearings for the mazdaspeed disi motor. .025 and .05 over for the main and .025 over for the connecting rods.

Can anyone else verify this?

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Here is a link for the mains:

STD
OS .25
OS .50

1100A - PISTON, CRANKSHAFT & FLYWHEEL. Fits: 2007 Mazda MazdaSpeed6 | Jim Ellis Mazda

I am in the process of having some connecting rod bearings done by ACL. So those will be available soon.

Here are the sizes that are available for the mains from ACL now:

STD
.25
.50
.75

Part number 5M8174A

Jason

And by oversize we mean that the bore the bearings create is undersize?

Yes, basically allows the crank to be machined if necessary. For a long time these weren't available

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I was just about to say that the .50s were not available anymore as i think that is why dustin had his problem.

stuck

Since it is stuck now, here are the part numbers if someone wanted to use Clevite or Federal Mogul or King as an option. Some people like to have other options:

Mains:

Clevite 77: MS-2245AL
Federal Mogul: 7411MA
King: MB5442SI

Jason

I was just in the process of starting the same project with King Bearings for Rod Bearings.

I just posted the oversize bearing part numbers in my ms6 part number thread. I couldnt find them forever but I finally found them for the crank, rod, and thrust bearing.

PLEASE post in here!!!!!!

Alright, thought that I would update everyone about the con rod bearings. ACL actually had them already. They are the same ones that are used on the Mitsubishi 4B11T 2.0L motor. Here are the part numbers for not only ACL, but Clevite 77 interchanges if you are interested:

ACL: 4B1236H
Clevite: CB1918H

That is the "standard" part number for the ACL and Clevite. ACL has the .025, .25, and the "X" which have an additional .001".

Jason

And by oversize we mean that the bore the bearings create is undersize?




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Ummm....
You trolling me nigga?

When the crank is machined, it's journals have metal removed, thus making each journal's outside diameter smaller. Thus the replacement bearings must be oversize, with a larger assembled inside diameter to maintain specified clearance. To my knowledge, no bearing manufacturer makes smaller than stock rod or main bearings.

Of necessity, they will be either standard or oversize.

BTW: if bearings are now available (mains and rods) from Clevite, that company's uniform quality is superb. You really can't do better than Clevite 77.

If the crank journal is smaller, and the bore the bearing makes is bigger, your clearances are growing.

You cannot remove material from the crank, and the bearing bore and expect clearances to be maintained.
The term oversized, refers to the thickness of the bearing halves.

I think u guys are saying the same thing in different ways...

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^ Exactly! The backing of bearing shells will the thicker and the O.D. of the bearing surfaces when combined will be larger to compensate for the loss of metal on the crank journals.

In an earlier part of my life and growing up in an automotive/industrial/diesel production engine rebuilding company and machine shop, I spent a LOT of time at the controls of crankshaft grinders, rod reconditioning machines, cylinder boring bars, milling machines, etc., and in assembly of short blocks and cylinder heads. About the only machine I did not have time to learn to operate before my journey through business school and a post-graduate degree was the camshaft grinder and the development of the lobe blank masters for custom (read: performance) grinds.

I am still very much involved in that business, but now on the management side.

Main Crankshaft Bearings: Use Oversized or Undersized Bearing

There ya go

He said larger inside diametre. That's not the same as smaller inside diametre.

^ You are right. The assembled I.D. of the bearings must be smaller to match the smaller journal size (plus the oil clearance). Misstatement brain fart in my first post, corrected above.

Discuss Here: http://www.mazdaspeedforum.org/forum/foru...arings-103197/