Oil pressure drops to 0

While the distributor is out, and oil pressure port removed, I primed the oil system with this contraption and made a huge mess when it came blowing out of the port. I then hooked the gauge back up and primed the oil system for probably 45 seconds at 70psi and it didn’t drop at all. I’m going to reassemble everything and fire it up to see if it still does it.
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