[crank182]

Watch the engine when it warms up. You might have just got some oil on the exhaust that is burning off. If it's coming from the side of the engine below the heads thats probably all it is and it'll stop smoking once it burns off. Also like was said above you can re-use the old rubber seal and don't need any sealer or anything as long as it isn't cracked or broken but they are pretty cheap and since the valve covers are off you might as well replace the seals anyway. If the valve cover isn't sealed right it will leak oil and it'll end up on the exhaust causing a lot of smoke. I know the valve covers can be a pain but once it's in place you can lift it up and feel around the bottom to make sure the seal is in place. Hope this helps.