The Moroso racing filter is a good one. I had the same problem using Milodon oil pump. The O ring on the oil pump snout that goes into the block seemed to be leaking. Every time i changed oil and filter i lost prime. Its the only place i could figure it might suck air. I put a little rtv on the O ring and slid it back up in there. Dont use alot of rtv, because a clump of that could get in the pump and lock it up. You could also try a bigger O ring if you can get it to fit.