I tend to abuse my engines. Being hard on any machine tends to get one looking for a way to reduce frequency of failure. Many of the 22R engines I've torn down had perfect main bearings with rod bearings showing much more wear, or even failure.
Most suggest chamferring the oil hole in the crank journal. That chamfer does well enough in guaranteeing oil supply to the rod bearing, but I still want a bit more. In 4AGEs this mod reduced the frequency of the rod failures I've experienced. Most of those failures were in engines that regulrly saw RPM in excess of 9000rpm. Then I found ACL race bearings have a 3/4 diameter groove that covers the issue very well. Might just end up having the lower bearing shells machined to make a 3/4 groove.
Bearing failure frquency I've seen is, greatest to least, rod bearing, thrust bearing and then main bearings. Thrust bearing failures have been primarily in manual tranny set-ups.
