My take on the oiling system crossover tube for the small block

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Beneath the set screw, I drilled a small hole in to the main oil galley to feed the passage full time. To feed the left side you would replace the set screw with a fitting and put a line from it to the left side passage.
Be very careful when drilling into the main galley to line up correctly or you will hit the water jacket.
Pretty big chamfers at the top of those lifter bores, I heard those type bores leak huge.