ORIGINAL: earlwb
I sorta like where they drill the oil hole on the top facing the intake hole in the crankshaft. That way it gets more fresh oil coming in more cool and hits the crankshaft on the way into the crankcase. This example is from a old Irvine .61 engine. But the oil hole could be either way, top of bottom as both methods work. I am not that fond of the narrow slit or cut in the rod. I see that as a point for failure as it weakens the rod more, but that would be with high RPMs or higher stress situations where it would be a issue.
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This hole is not right placed as you showed the pic of drilled oil hole in con-rod and see this link why the idea to drill a hole there is pressure zone is a bad idea:
http://www.tribology-abc.com/abc/tower.htm
I had never seen the engine been damaged by slitted recess for oil in the bottom of connecting rod. I has some model engines with slitted recess in connecting rod, in fact there is not much load in running condition.
See the pic..
In the engine who has a oil hole placed on the top of con-rod has own oil pump to give continous oil pressure whole time as you find in the automobile car engine to example..
The purpose with the oil hole placed on the top of con-rod to lubricate the pressure zone between the cylinder and piston before the piston goes down during the combustion period.
Edit: forgotten to write more..