I ran into rod bearing problems when assembling a 1990 3.6 911 engine. All stock, crank polished, rods checked and sized. When I put the rods on the crank, several wouldn't turn. Disassembled and sent the rods back to the machine shop to recheck. They were in spec. After looking online, and finding posts about several "issues" with glyco rod bearings, I checked them all. Also obtained a set of clevite bearings, they are the darker ones in the photos. This is what I found:
First picture is both sets of bearings, I numbered the glycos as I took them out of the engine after the test assembly, the clevites are just numbered to keep track of them the same way:
This is how the measurements were made. The measurements at the parting line were all done with the pin the same distance from the edge. This is important because the the clevites have substantial taper to the edge. Exactly like a rod bearing is supposed to.
Glyco measurements. Note that the pin is 0.3745" and must be subtracted for actual dimensions. The right column is the flat side of the bearing, the left colimn is the side with the locating tang, and the middle is the middle.
Clevite measurements.
WOW what a difference
The glycos varied all over the place. A couple were probably ok, but some of the worst are positively ridiculous. There are a couple with 0.010 side to side difference. Also several with the parting line thicker than the middle of the bearing, opposite the way it should be. Rod bearings have eccentricity designed in, the middle of the bearing is supposed to be thickest, with a taper at the parting line to account for rod stretch. The clevites in comparison were essentially perfect given the limitations of my measuring equipment. They were all in the range of 0.0002
The glyco's were dated 05-14, and the box had a sticker Made in SAfrica.
I have always measured bearings when assembling engines, and can't recall ever finding any bad ones. Got a little lazy this time and it almost bit me, be careful. Also another reason to get good rod bolts, engines don't always go together the first time. It might also be of interest that the number stamped into the clevite bearings doesn't show up in any clevite catalog. I assume they are specially made. My conclusion is pay the money and get the good bearings. BTW, Mike @ Memphis Motor Werks did a great job helping me out with quick turnaround, and quality machine work.