well bbc have good drain back even with a stock pan with a hv pump a short blast you not sucking the pan dry . on race engine 20w50w val or straight 40w is what i like as long as it warmed up good be for you beat on it . i use the brad pen 40w . i would stick by the oil getting hot as well . i build alot of bbc so i should know . soon has my skin grows on my back i be building more i know where to set the mains and rods so i do not get calls on low oil PSI . by pass could of got hanged up .the oil could of been breaking down as well