[at2pt]

I own a 1987 924s that in the past year had the top end rebuilt. Ever since i purchased the car there is no oil pressure on start up. I have tried 10w-40, 15-40 and i currently use castrol 20w-50. Temperature seems to have no effect, only time. If the car sits for less than an hour, the pressure will go back up immediately, but much more than that and it takes up to 30 seconds to get pressure. This led me to believe it was not having an anti-drainback valve on the oil filter, but i have tried all different types of filters to include the original equipment, nothing works. Any suggestions would be appreciated if i can't figure it out i will be forced to by a pre-oiler and i am not looking forward to that.