226/6 problem

I just started working on my 71 Scamp. My HOA wants to tow it away because it is not registered. I stoppped working on it 10 years ago after insatlling the head, timing chain, distributor, new wires, water and pump. The 225 / 6 still runs like crap. The motor spits out black smoke anf the air filter gets dirty fast.Not sure what is wrong. I just took off the intake and exhaust manifold and am hoping this was the problem. Anyone have any thoughts?