I've got a 216 block on a stand in the shop right now, but my oxygen hose won't reach that far! As soon as I can, I'll check the oil circuit. I hadn't seen the pics of the filter when I mentioned the canister filter. For a 216 pump to develop that kind of pressure, there had to be a major restriction somewhere, probably upstream of the rod squirt tubes. The squirt tube manifold is in the oil pan, and there's a separate oil nipple that supplies it. The mains and cam bearings get lubed off the oil gallery that runs the length of the block.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!