The oil filter canster on my 8N leaks from the top, where the bolt goes down through. None the oil filters I have been getting for it,[Napa, or wix 1010] have a big oring, for the cap, but not a small one for the bolt. What should be there? Is is a gasket, like a drain plug has, or an oring? Any one know what size? I have to do an oil change anyway on it, and want to fix this leak wile I have it apart.