After the oil leaves the oil pump, and travels through the transfer pipe on its way to the block, this is the first constriction that the oil must fight and overcome on its way to providing needed lubrication.

Reaching down inside the passage with a long shank carbide burr on the die grinder to remove that step is fairly easy to do.

Taking a decent picture of the results of the step removal after the work is done is not.

Maybe, now that I have since acquired a tripod, I might be able to take such pictures in the future.