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

[dwcsr]

Check the float level. make sure the jets are tight and the float needle seat is good.

[68gmsee]

Welcome from the state of Tx where the Aggies got a whipping and the boys lost. Two bad days in a row. : (

Yeah, check the float level. Easy to do on these monojets, of course. But also make absolutely sure it is indeed black smoke you're seeing. Make sure it doesn't have bluish tint to it when looking at in the sunlight.

Dark gray to blackish gray is usually a rich condition, but sometime oil burning will look like that too. It depends on the lighting. You may have bad valve guides if only does it when you first crank it up and has that bluish tint.

You didn't mention what type of choke you have but if it's automatic you might adjust it until its wide open and try that way..

Keep us posted.