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      10-14-2013, 03:13 PM   #245
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Drives: E92
Join Date: May 2012
Location: Charlotte NC

iTrader: (9)

Regular Guy was gratious enough to send me bearings to look at and measure and hardness test.
What has been observed is the original 088/089 bearings are a copper/lead content while the 702/703 bearings are of an aluminized tin/silicon compound.
Measurements with my mic are as follows, I am in no way saying what is right or wrong but there is always a tenth or two between different people, just because I measure one way is not to say another measurement is incorrect. What matters is the same guy measuring the crank and the clearance for the final outcome.
088 .07875
089 .07885
091 .0837
090 .0836
702 .07855
703 .07875
Measurements are pretty much in line with what others have documented up until they get polished.
What is a MASSIVE change is the hardness of the bearings. I will not get into the difference of what is right or wrong here but just know the new 702/703 bearings are a huge jump in hardness
The average hardness for the 088/089 bearings are the same at 16.2B Scale
The average hardness for the 702-703 bearings are the same at 61.8B Scale

This puts to rest the theory that one bearing is harder than the other relative to the old vs new ones.
We can work bearings to get a few tenths when needed at our shop. The big one here is not only are we gaining on the average .0002-.0003 by going to the 702/703 but we are also gaining .0003 more by our polishing method. In essence a rod that was .001 clearance before with 088-089 can now be installed with the newer polished bearings and be AROUND .0016. Bearings that were in at .0013 should be able to get to .0019. It is not the end all be all but it will help.
Also remember I have one smaple of each bearing. From our experience ther can be +-.0001 from shell to shell. Not every bearing will turn out the same as these measurements. Here are some pics for comparison. I did not do pictures of the before polishing sizes, they were measured but not photographed.
Attached Images
Electronics Junkie, Engine Builder.

Last edited by kawasaki00; 10-14-2013 at 03:20 PM.