tube identification

[Adodero]

There is a tube poking out of our engine that's been capped off, its letting out a small amount of smoke here and there, so I'd like to know what it is and if that's a problem.

The tube is between the valve cover and the carb, I've attached a picture, you can see it with the bolt stuck in the tube. What is this tube called and why would it be releasing a small amount of smoke?

 

[Torxhead]

I can't quite see the tube, but I do see the head of a bolt. Is this black smoke blow-by from the hot engine oil and tired piston rings or is it from the exaust? If it is blow-by, it should be coming from the chrome breather cap on top of the valve cover. It could be exaust gas coming from an exaust manifold emissions tube.

 

[MadCJ95]

The tube is for the choke on the factory carb (the one with to bolt on top); from the factory there should be a metal hose running from that tube to a plastic housing with a spring, the heat "weakens" the spring to allow the choke to open. When I swapped my Carter BBD out for a MC2100 I plugged it with a bolt, very similar to yours.