Technical What are these bearings?

I know (or at least I think I know) That these are 59a mains but what does the red- blue mean? I was looking for standard bearings for a 59a
ICM 6333 A
Red .0852 - .0855
Blue .0855 - .0858

Is what is says on the box
Thanks for your help

 

The colours are factory code for different tolerances on the same nominal size. Allows you to get the bearing clearance spot on. Im surprised they were doing it that far back.

 

I still don't understand. Are the red and blue plastic gauge colors?

 

Kind of. I’ll try and explain better. I don’t know the journal size without looking it up so these numbers are just for example.

Standard journal size is 2.5000”

For journals you measure as say 2.5000” to 2.5005”you would use a red bearing, if you measure 2.4995” to 2.5000” you use a blue. But the part number is the same. There’s usual only a thou or so difference. If you’re going undersize you polish to tolerance but in the factory they did it by using one or other bearing. In modern engines there can be 4 or 5 different colours from the factory.

The factory repair book will have the tolerances.

 

This example is for a 61 Mercury.

 

I've found similar bearings in some of the countless small block Chevrolets I've dis***embled over the years, with one off sizes like .0006 and .0012.

 

Learn summink every day! I'll admit it I tend to keep away from engine internals as much as possible, but it feels strange that after fiddling with stuff for over 50 years I didn't know anything about such bearings! Always wondered what to do if a bearing came up tight when plastigauge checked. Now I know. Something else to add to the ageing / failing memory!

Chris