1979 dodge ram van 5.2L smoke problem!!!?

[boardguy2008]

ok I have a dodge ram van and I notice the every time a start the engine there is a lot of black smoke,but after a while it goes away, if I shut it off when it starts again its the same thing.....black smoke then nothing
due to this problem it can't pass the smoke check
does anybody have an idea of what could be the problem and how much could cost me