ED
soot in exhaust
Thread Starter
Racer
Joined: May 2007
Posts: 370
Likes: 0
From: Cherry Hill N.J.
soot in exhaust
77 -350,edelbrock 1406, timing advance 14 degrees @750 Rpm, 32 degrees@2600 rpm, 51 degrees @ 5000 RPM... new plugs, wires......
car idles and runs great......no misses, no hesitation...no gas odor...
sounds good? Why is soot (excessive unburned fuel) forming on interior
of tail pipes........
car idles and runs great......no misses, no hesitation...no gas odor...
sounds good? Why is soot (excessive unburned fuel) forming on interior
of tail pipes........
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Timing will have an effect, but what you should be chasing is carb mixture.
I'm not familiar with tuning an Edelbrock, but I'd imagine that primary metering rods are what you're after. Are you seeing black smoke at idle only, or idle+cruise? Actually, a little blackness on the inside of your tailpipes is not worrisome.
It's black smoke you should be concerned about. Use a wideband or smog sensor.
I'm not familiar with tuning an Edelbrock, but I'd imagine that primary metering rods are what you're after. Are you seeing black smoke at idle only, or idle+cruise? Actually, a little blackness on the inside of your tailpipes is not worrisome.
It's black smoke you should be concerned about. Use a wideband or smog sensor.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
If you're running current pump gas with 10% federally mandated ethanol, the inside of the tailpipes will be black and sooty no matter how you tune the engine. If you want the pipes to turn light grey, go put a tank of $12/gal race gas with no ethanol in the car and enjoy the color... We see black exhaust components using ethanol-"enhanced" pump gas even on the dyno with the engine absolutely optimized and running with red-glowing headers. Nothing you can do about it as long as the corn-growers' lobby is making you run ethanol in the fuel.
Lars
Lars
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Thread Starter
Racer
Joined: May 2007
Posts: 370
Likes: 0
From: Cherry Hill N.J.
As usual, Lars, you are the man!!!
I was looking for a problem that does not exist.....
I guess now I will look for something else to "FIX"!!
It is a disease we all suffer from.
Thanks!
I was looking for a problem that does not exist.....
I guess now I will look for something else to "FIX"!!
It is a disease we all suffer from.
Thanks!
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Soot coating the exhaust tips is normal. (see post 5)
Black exhaust smoke is not, that's an indicator of running heavy rich.
If you are interested in knowing where you are, start with a gas analyzer tool. Then, finalize with a dyno or a stopwatch.
There are other techniques as well, but I'm not familiar with the Carter style carbs.
A car will run very smoothly and still leave power on the table.
Last edited by Shark Racer; Aug 17, 2012 at 11:37 PM.
6th Gear
Joined: Sep 2018
Posts: 6
Likes: 1
From: Wollongong New South Wales AUSTRALIA
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
I can't remember what I was on about back then - try car wash soap, if that doesn't work, then a clay bar, then polish. Try to minimize soot by making sure your car is well-tuned, and also the outlets of your exhaust system should clear the bumper by a bit. If the tips abort too close to the paint work the panel will soot up.
Le Mans Master
Joined: May 2007
Posts: 5,028
Likes: 1,120
From: North tonawanda NY
If you're running current pump gas with 10% federally mandated ethanol, the inside of the tailpipes will be black and sooty no matter how you tune the engine. If you want the pipes to turn light grey, go put a tank of $12/gal race gas with no ethanol in the car and enjoy the color... We see black exhaust components using ethanol-"enhanced" pump gas even on the dyno with the engine absolutely optimized and running with red-glowing headers. Nothing you can do about it as long as the corn-growers' lobby is making you run ethanol in the fuel.
Lars
Lars
I believe this depends on where you live. Around here they sell ethanol free premium gas at many gas stations its what I use 99% of the time.
Last edited by augiedoggy; Nov 17, 2020 at 08:04 AM.