The only engines that have an "oil line" through the block are pre-1954 splash oiler 216's and 235's with the oil distributor on the driver's side of the block. Later model engines have drilled passages in the block which can also clog up and restrict oil flow to the head.

One possible quick fix is to remove the center head bolt on the passenger's side and insert a snug-fitting wooden dowel into the hole after filling the hole with oil. Then smack the top of the dowel HARD with a BFH. Sometimes the hydraulic pressure created by the hammer lick will purge the crud out of the oil passages and restore the flow. I have fixed several slow or no oil flow engines that way.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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