250 and Black Smoke

[fnla39]

I've got a '70 250 with a monojet Carb. It starts and idles great but when I rev it up thick black smoke is what I get. It's in time and like I said starts without hesitation. The jet init is a 106 I put another in it that was a 102 and noticed a slight difference but not much. The fuel air screw has been adjusted fron 1/2 to 1 1/2 out with no change. I have fouled out a set of plugs and now I am at a standstill. Any suggestions? Thanks