440 engine oil pump loses its prime when it sits even for a couple hours and takes 1-2 seconds for it to build pressure, once it builds pressure it is fine and never waivers one bit. I have a mechanical gauge and an idiot light and they both go off at the same exact time. When I take off the filter it is empty and I have put 2 new wix filters and one amsoil filter on with anti-siphon flaps and they all do the exact same thing. At first I thought it was the oil pump and replaced it with a new melling high pressure pump which is what I have had on it for the last 30 years and never had a problem. My valve covers have breathers on them so I don't think its like a vacuum situation drawing the oil out. Is it possible the new filters can't handle the presssure? or is there a better filter?. This is very puzzling to say the least as it came out of the blue this year and this engine has about 25K on it 30 years off use. Any thought would be appreciated. Thanks, Lou