I am rebuiding my 1937 248 engine. The rear main bearing cap has a drain hole in it that lets oil drain back down into the enigine pan. There is 1/8" drive pin that can be seen sticking down inside the drain hole. Was this pin used to affix a piece of tubing to help direct oil into the pan? The guys at the machine shop wonderd if ths pin was put in to keep a ball bearing in place, that would act as a check valve to keep oil from going from the pan back up into the rear main when you are going up a steep grade when all the pan oil goes to the rear of the pan. Does anyone know if the rear main cap has a ball check in it or a tube to direct the flow of oil from the rear main. Or, is there nothing but a unobstructed hole in the rear main cap which lets oil flow into the pan. Thanks guys for your help!!