Hollow push rods

I also recently refreshed engine bearings and such. New comp cam, Hydr. roller lifters #8921, magnum rockers. the new p-rods #7174's also "hollow" 3/8 x 5/16 cup/ball. I have HV oil pump, 7qt. pan additional oil for hv-pump. Oil pressure at start up is stead at 60lbs. until temp is at 180 for a bit and the pressure IDLE drops close to zero, i have to keep the rev's up. Could the hollow p-rods be the cause?