lost oil pressure

Ok, pulled the intake and valley. #3 intake lifter laying in the valley, pushrod not bent, roller rocker ok. Had this happen on a Ford 300 6 years ago, all I could figure out was the lifter collapsed over night, giving the clearance to toss the pushrod.

But this happened within 1/2 hour, while we changed springs on the Eddy carb. Any suggestions. experiences? 400 miles on all new parts.