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Discussion Starter #1
I recently put a holley 600 on my sbc350. The problem I'm having is the left tail pipe of my dual exhaust is puffing out black smoke. Its not real bad, but it definetly stands out compared to the right tail pipe, which is fine. My guess would be the cylinder(s) on the left are getting a rich mixture, but I don't know why or what causes this. I equally adjusted my mixture screws.

What could be the cause of this black smoke on one side?

thanks,
mark
 

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Hates: Liver. Loves: Diesel
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Mixture screws only affect idle mix. The amount they would affect mixture at other points is completely neglegible.

Sounds like you have a float setting too high and its dripping raw fuel in one side, or maybe you have a mismatched jet setup. I'm not too familiar with Holleys, but it sounds like something on that side is dripping raw fuel into the intake.
 

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Discussion Starter #3
well, no black smoke now, I'm not sure if there was actual black smoke when I posted my first question, cause its hard to tell when its freezing outside. Alls I know is theres thicker smoke coming out of my left tailpipe. Its really cold right now where I live and you can tell the exhaust is thicker on the left side. Almost like if the left tailpipe is hotter than the right. I rebuilt my Holley before I put it on my 350. But my exhaust never did this with my q-jet on.

Any suggestions of why its doing this are appreciated,
Mark
 

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There is almost no way that a carburetor can make one tailpipe blow black smoke and the other NOT.

If it is a dual plane intake, one side of the carb feeds 2 cylinders on each side of the engine.
If it is a single plane intake, all 8 feed from the same common plenum.

You have a serious problem if only one side is smoking.

Need more information.

If you have stock exhaust manifolds then your heat riser valve is working correctly pushing most of the exhaust out one side.
Remember I said..... almost no way?
 

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xntrik said:
There is almost no way that a carburetor can make one tailpipe blow black smoke and the other NOT.

If it is a dual plane intake, one side of the carb feeds 2 cylinders on each side of the engine.
If it is a single plane intake, all 8 feed from the same common plenum.
I've had it happen to me before. If its leaking out of one corner of the carb, it could only feeding one bank.
 

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xntrik said:
If you have stock exhaust manifolds then your heat riser valve is working correctly pushing most of the exhaust out one side.
Remember I said..... almost no way?
i think you nailed it. i was just about to post that when i read your post.

after the car warms up the valve will open and exhasut will be even out both sides. but when cold it cuts off the right exhaust and sends the exhaust threw the intake and out the left exhaust pipe.
 

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curtis73 said:
I've had it happen to me before. If its leaking out of one corner of the carb, it could only feeding one bank.
That is very serious flooding and very poor fuel distribution problems. (More likely in single plane intakes.) Usually floods downhill to the rear cylinder. Something that bad would likely cause a noticable miss, that would be traceable by soaking wet spark plugs.
 

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Agree with the heat riser at this point. Run a finger in the tailpipe and see if you got more soot/carbon on the suspect side.

Here in Manitoba it's -37 F below and the winshield is somewhere at -44 F, today. Just to get some heat I'd be holding my hands on the side with more exhaust.
 

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Discussion Starter #10
thanks everyone for your replies. Well, when I got home I was checking my timeing, and I noticed I forgot to tighten the dizzy hold-down bolt. My dizzy was loose the whole time, making my truck run like ****, because the timeing was off. I'm such an idiot, lol. Anywase I set my idle mixture screws equally and set my timing good. It runs good now, and now I have an equal amount of exhaust on both sides. What ever I did, it fixed the exhaust problem. Thankyou everyone.
Mark
 
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