Classic/Antique Car Repair: smoke from exhaust manifold bolt, chev 350, bolt head

Question
My 1973 chev 350 engine was a pro rebuild in 1991. Runs great. It has begun to produce smoke from the drivers side rear bolt of the exhaust manifold into the engine compartment. I thought the valve cover might be leaking but it appears to be coming right from the bolt head. There's some oil on the whole side of the block but the manifold appears to be dry. Any advice greatly appreciated!

Answer
If it is truly a leak out the bolt hole,  then your gasket has blown through to the hole. No real big deal unless it starts "cutting" and it would be pretty loud at that point.

I have stopped this with a copper washer on the exhaust bolt.

BUT, understand if you are blowing smoke out the bolt, you are blowing smoke out the back of the car. If your engine is not smoking, you have a sneaky oil leak you just aren't seeing.