Been doing a bit of homework on bearings and found an interesting article by Mahle.
It states....
" Many early engines used full grooved bearings and some even used multiple grooves. Those choices were based on what engineers knew at the time. As engine and bearing technology developed, the negative effect of grooving was recognized and bearing grooving was removed from modern lower main bearings. The result is in a thicker film of oil for the shaft to ride on. This provides a greater safety margin and improved bearing life. Upper main shells, which see
lower loads than the lowers, and hence don’t apply the same load to the oil film, have retained a groove to supply the connecting rods with oil. "
So I presume BMW built engines with grooved lower bearings and then moved to smooth shells. I seem to have the early version.
I've thought of Option 3 - very carefully grind or file off the extra indent on the new smooth bearings. And grind slowly to avoid any build up of heat?
Any downsides to this option?
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