espskillz

I just recently had a mechanic tune my carb and he asked it i wanted it to be for preformance and i told him yea. so he went ahead and tuned it and made the choke stay open all the time and said that it more air you get it the better preformance you get. but when its sorta cold and i floor it black smoke comes out of my exhaust. i was just wondering if that is bad for the car and if i should adjust the choke to work?

Soaring

Dumb mechanic. After your engine gets warmed up and your butterfly is all the way open, it does not restrict any air flow. You need the choke to be closed at start-up so you can get the engine running. Black smoke indicates the rings are worn and the engine is burning oil. That has nothing to do with your carburetor.

paddy187

I have no choke on my carb PO took it off the choke butter will restrict air flow slightly, the block smoke to me means over rich mix which would make sense for a bad performance tune.

grruminator78

black smoke, well what it could be depends on a few things, check the pavement when you stomp the gas, does it leave carbon on the pavement?

espskillz

yea ive seen it do that but not every time i floor it will it leave carbon on the ground but yea i took a look at my holley manual and it said if the choke comes off too soon it will produce black smoke and staying on to long will produce backfires. so im gona go ahead and re-tune my choke i mean it was put on there for a reason mind as well use it.

grruminator78

just start doing it all yourself, carb tuning is not very complicated

rmodel65

black smoke means your running rich not burning oil your just dumping to much fuel at idle

oil burning smoke is blue and
water is usually a white as in steam

Soaring

Yeah, I know everybody says oil burning is blue and rich gas mixture is black, but the only way I have ever been successful in telling the difference is to actually smell the exhaust fumes. Not but just one little whiff though. You can smell if it is gas or oil. And, if it is oil, it may or may not be the oil rings. It could be the valve stem seals.
This isn't really conclusive and probably more often is a sign of worn rings. The usual manifestation is that the engine starts up ok, but as soon as the RPM is raised much above idle, the smoke starts rolling out, the reason being that the cold, worn rings are unable to seal against the oil sprayed on the cylinder walls when the engine speed is raised. The smoke tends to subside to some degree as the engine warms up and the rings and piston expand into the cylinder. A somewhat better quick check of the valve stem seals is to drive the car until the engine is warmed up, then let it idle for a fairly long period, say 3-4 minutes. This challenges the stem seals with high intake manifold vacuum, but does not tax the rings so much since there is relatively little oil being applied to the cylinder walls at idle. Now step smartly on the gas and drive away. If you are being followed by a smokescreen worthy of James Bond, it's a safe bet the valve stem seals are shot. Remember that all these external check are just indicators, and that often, the stem seals and piston rings are BOTH worn