I'm not sure about the drain back holes on my shp block, I'll have to check. I have an oil pan with a windage tray on order, I think I'm better off with a windage tray in the pan than without one in it, so I ordered one, but the car has run fine up until now ( on the street and at the track ) without a windage tray in the pan, so I don't know why the pan without a windage tray worked before but doesn't work now. I'll try out the new pan when it's delivered and see what happens.