i just had my 78 350 olds rebuilt and i am starting it for the first time. for some reason i have coolant leaking from one little spot on my valve cover. it is right above the #6 sparkplug. it drips down onto my exhaust manifold and causes alot of smoke. it only does this when the car is running and for about 2 minute after i turn it off. can someone please help me. i have put to much money into this car and cant afford to lose it right now. i could not find any cracks. car runs fine.