my 408 & my 418 have both been very slow building oil pressure at start up. win. block, SVO- N heads,full roller system, 4340 crank, H-beam rods, 11.7 pistons,melling hi-valume oil pump, rocker girdle, & main cap girdle, I allso use the thicker fel-pro racing head gaskets. I have wounderd if its the oil pump. every one I talk to doesnt have a clue. this makes me very nerves......! anyone out there have the answer as to why these engins have both done this. P.S. tried replacing oil pumps 3or4 times & oil psi. 50 to 60 depending on oil temp. also tryed differnt filters.