One of the headaches of the 216 "gotchas".
One of the guys at chevytalk made a demo of what it looks like.
From the oil pump to the rocker arm assembly, the oil line travels through the water jacket.
You can purchase a repair kit from classic car and truck suppliers.
https://www.chevytalk.org/fusionbb/fbbuploads/1491615924-condensed_top_oiler.jpg


"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."