Are these (new) bearings OK to use?

ohecht · 03-25-2014, 09:06 PM

I'm just starting the assembly phase of my 3.2 SS rebuild, and wanted to get some opinions on the state of the new bearings I have. They are part number 99610190101, GT3 "Yellow" bearings. The packaging indicates they are Goetze parts. As you can see in the pictures, there seems to be a uniform marking along the side of each bearing...it almost looks like something is on the surface of the bearing...either that or very light scratching.

The one on the end is the one that the machine shop opened up as part of the cross-drilling for the crank, and that one looks like the entire coating was removed, maybe as they deburred the hole? That one has me worried, since I'm not sure if the visible greay coating is designed to wear off quickly during break in and the others will then look like the drilled one, or if the grey coating is the actual bearing material that needs to be all there and as uniform as possible.

Thanks in advance.

Olivier

KTL · 03-26-2014, 07:49 AM

The grey coating is very very thin and very very fragile/sensitive. When I measure bearings with the bore gauge, the anvils (which apply very little pressure) easily rub the coating off the bearing.

I recently measured some no. 8 crank bearing inserts new vs. old/used and they both measured the same in the bore gauge. That was despite the old one looking "worn" where the silvery coating was rubbed off in one region of the bearing surface. So the coating is thinner than 0.0005" because that was the resolution of the indicator in the bore gauge I was using. I have a 0.0001" increment dial indicator that I wanted to use for further comparative measuring but forgot to follow up on that....

The new hole in the no. 4 main bearing looks pretty big. How large did they drill it out?

ohecht · 03-26-2014, 06:27 PM

Thanks Kevin. The enlarged hole should be 6mm. I talked to the machine shop today and they told me that the grey coating was just a coating to prevent oxidation of the bearing surfaces and was not actually part of the bearing surface. That could make sense based on your measurements, too...

IXjamesXI · 03-27-2014, 03:54 AM

I also recently bought a set of Std (yellow) GT3 bearings and they look identical to yours. I was assured that they are good-to-go despite looking very inconsistent in the coating. They certainly feel smooth, and checking the "thickness" of them with a mic against some used bearings seemed ok. I am tempted to send them to Calico for coating anyway.. they do look unusual compared to how I expect a bearing to look, but maybe its just how the final wash / coating / whatever dries on there. I wish I knew more about how these things are made.

IXjamesXI · 03-27-2014, 04:17 AM

GT3 Crank Bearings.. do these look ok?

71scgc · 03-28-2014, 05:35 AM

I recently built a 400ci Chevy SB. Used Mahle Mains in it.
Looked like these, exactly.

Carter

Henry Schmidt · Henry Schmidt's Garage

Because of the low quality of the bearings we see today (as your pictures illustrate) we just send them to Calico Coatings for their CT1 process. Moly +oil has a far lower friction coefficient than any non coated bearing on the market plus dry film moly is capable of resisting pressures in excess of 350,000 psi.

Calico Coatings

ohecht · 03-28-2014, 08:08 AM

Thanks Henry. I was considering the same thing since I don't want to start off on the wrong foot here. Do I need to worry about the clearances changing? Calico did say that their coating added a measurable amount of material to the surface but I'm not sure if it would impact the bearing clearances overall.

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally Posted by ohecht

Thanks Henry. I was considering the same thing since I don't want to start off on the wrong foot here. Do I need to worry about the clearances changing? Calico did say that their coating added a measurable amount of material to the surface but I'm not sure if it would impact the bearing clearances overall.

It does reduce the clearance (.0002 to .00035) on bearings but if you have a used crank, I think you'll find that your crank will measure at the low end of the allowable spec.