Let's find out what 702/703 rod bearings are really made of
If this post is still up and doesn't say otherwise, we're still looking. There's no hurry and no deadline.
Some key initial assumptions about 702/703 bearings have turned out to be questionable. It was thought that these were bimetal bearings with the top layer being an aluminum/tin alloy, and that oil analysis couldn't meaningfully track their wear because they only contained elements that were abundant in other wear surfaces in the engine. While these were reasonable assumptions based on the info that was out there, they do not appear to have been based on an indepth physical analysis of the bearings, and wear patterns and close-ups suggest that the bearings might actually have some kind of trimetal construction. If that's true, we may have to revisit a lot of what we think we know.
The way to figure this out for real is to send a pair of 702/703 shells to a lab. The lab I spoke with, Element, quoted me some numbers:
$151.50 per bearing to get the number and thicknesses of the layers via optical microscopy (micron resolution)
$341.78 per bearing to get a "semi-quantitative" elemental analysis -- basically what elements are in each layer, and roughly at what levels (a lot / a little / trace)
Bearing shells are $43.16 each on FCP Euro.
Would need to be done for both shells to make sure they're made of the same stuff. So, about $1073 all-in.
Far too much for me to feel like it's worth doing myself, but a pittance if crowdfunded. If you'd like to contribute, please post here.
Some key initial assumptions about 702/703 bearings have turned out to be questionable. It was thought that these were bimetal bearings with the top layer being an aluminum/tin alloy, and that oil analysis couldn't meaningfully track their wear because they only contained elements that were abundant in other wear surfaces in the engine. While these were reasonable assumptions based on the info that was out there, they do not appear to have been based on an indepth physical analysis of the bearings, and wear patterns and close-ups suggest that the bearings might actually have some kind of trimetal construction. If that's true, we may have to revisit a lot of what we think we know.
The way to figure this out for real is to send a pair of 702/703 shells to a lab. The lab I spoke with, Element, quoted me some numbers:
$151.50 per bearing to get the number and thicknesses of the layers via optical microscopy (micron resolution)
$341.78 per bearing to get a "semi-quantitative" elemental analysis -- basically what elements are in each layer, and roughly at what levels (a lot / a little / trace)
Bearing shells are $43.16 each on FCP Euro.
Would need to be done for both shells to make sure they're made of the same stuff. So, about $1073 all-in.
Far too much for me to feel like it's worth doing myself, but a pittance if crowdfunded. If you'd like to contribute, please post here.