I bulit a 427, 454 block 3.76 crank 2 piece seal with rtv on the cap corners for my 65 pick-up. broke it in with break in oil no leaks. drained it and put in synthetic for flat lifters. now after running a little i have a very small drip on the bottom of the bellhousing. you think going back to reguler oil and running it somemore or just open it up and put a new seal in?