I have a 1930 closed cab pick-up. There is a machi
The hole you are seeing is actually a drain hole. A cotter pin is inserted through the hole from the top and the bottom of the cotter pin is bent slightly to hold it in place. The purpose of that cotter pin is to vibrate or move around to keep the drain hole open. The oil is probably coming from your rear main. You need to drop the oil pan and check the clearance in your rear main. You should have about .001 to .0015 clearance. Check the clearance with Plastigage, if you have more clearance than stated above, you need to pull some shims out of the rear main to tighten up the clearance. If the rear main has too much clearance, you will need to check your front and middle main bearings at the same time. Or, if the babbitt in the rear main bearing cap is broken or cracked, that will cause excessive oil to leak by as well. One last thing to check is that the oil passage and the oil drain tube are open and in tact. The tube is the piece of tubing that is about 4" long and is attached to the rear main bearing cap.