Black soot out of exhaust pipe

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cudajim

cudajim

cudajim
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I have a stock 225 engine with a 1bbl carb (rebuilt) and it seems to run just fine but I noticed the back of the exhaust pipe is really black and sooty (that's a technical term). Anyway, it does not seem normal to me so I wonder what's wrong. I am soon going to add a super-six setup so it may be a non-issue but I'm still wondering what the fix is.
 
usually means a very rich condition. a rich mixture ,stuck float or old spark plugs, etc. it probably smells like raw fuel. black=fuel, blue=oil, white=coolant or condensation/water
 
You're most likely running rich. You said rebuilt, is this a rebuilt original carb or a rebuilt remanufactured carb? Also is it a Holley 1920? I once had a remanufcatured Holley 1920 and one of the retainer rings in the power valve came out and the check ball was just rolling around in the float bowl. Every morning I would have a ton of black soot come out the tail pipe. You could even see a line of it down my driveway. I reseated the ring with the check ball inside and figured that was causing my rich problem since there was no check ball to stop the gas from flowing. After putting it together I had the same problem. Turns out it was just a junk carb (remanufactured).
 
The plugs are new. I rebuilt the carb and didn't notice anything out of the ordinary. The float works well as far as I can tell. No gas smell or anything else I can see.
 
You'd probably tell us if the car was blowing clouds of black smoke, so I'm guessing it's not. Keep in mind the tailpipe will be black and sooty on any car running on unleaded gasoline and not equipped with a catalytic converter (and many catalyst-equipped cars will also have sooty tailpipes, too). You very well may have no problem at all. If your fuel economy is normal and the spark plugs aren't turning black and sooty, there's probably nothing to worry about.

If you are in fact blowing clouds of black smoke or putting black skid marks on the driveway under the tailpipe, then more detail, please. What year is the engine, and how many miles are on it? What kind of carburetor is on it? "1bbl carb (rebuilt)" means...what? An original carb you rebuilt? A "remanufactured" unit from a parts store? How easy or difficult is the engine to start from cold, and how well does it run immediately after a cold start?
 
slantsixdan said:
You'd probably tell us if the car was blowing clouds of black smoke, so I'm guessing it's not. Keep in mind the tailpipe will be black and sooty on any car running on unleaded gasoline and not equipped with a catalytic converter (and many catalyst-equipped cars will also have sooty tailpipes, too). You very well may have no problem at all. If your fuel economy is normal and the spark plugs aren't turning black and sooty, there's probably nothing to worry about.

If you are in fact blowing clouds of black smoke or putting black skid marks on the driveway under the tailpipe, then more detail, please. What year is the engine, and how many miles are on it? What kind of carburetor is on it? "1bbl carb (rebuilt)" means...what? An original carb you rebuilt? A "remanufactured" unit from a parts store? How easy or difficult is the engine to start from cold, and how well does it run immediately after a cold start?
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Good points Dan. No, the car is not billowing black smoke, the output looks normal and no deposits on the driveway. It's a stock Holley car which I rebuilt. The spark plugs are burning normal and are not black. Everything inside was clean as a whistle. Fuel economy is ok and it runs well even when cold. The engine was "rebuilt" shortly before I got it. Since it doesn't leak or sound bad I have to assume it really was rebuilt. It's also pretty clean at the valve train. I had an old Valiant in the 70's and I don't recall the tailpipe looking black like this one.
 
the black residue could have been from the engine before it was rebuilt. unless the entire exhaust has been replaced when the engine was done.
 
My wife's 73 slant exhaust is a bit black on a cold start but clears up as the choke comes off and the engine gets some heat in it.
 
cudajim said:
No, the car is not billowing black smoke, the output looks normal and no deposits on the driveway. It's a stock Holley car which I rebuilt. The spark plugs are burning normal and are not black. Everything inside was clean as a whistle. Fuel economy is ok and it runs well even when cold.
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Then you haven't got a problem. File away the tune-up parts and technique suggestions in this thread for future reference, and keep driving.

I had an old Valiant in the 70's and I don't recall the tailpipe looking black like this one.
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…because in the '70s we were burning leaded gasoline, which when the mixture is correct leaves the tailpipe light grey.
 
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