BLACK smoke??
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Laughing Gas
Joined: Jul 2001
Posts: 849
Likes: 14
From: Fayetteville, NC
BLACK smoke??
Ok...I know blue smoke is caused by burning oil but what causes black smoke? I rebuilt the motor in Oct. and had the heads redone at the machine shop in town. I had to put another new carb on it about a month or so ago and ever since then the truck has a stumble in it when you pat the gas. I noticed yesterday when I pat the gas a few times back to back not only does it stumble but some black smoke comes out of the tail pipes. I don't run cats on it and I have a dual Flowmaster muffler set up which is only a year old. Any ideas? Seems like I remember from class that if black smoke comes out it is running either lean or rich....I can't remember which one it is though. What could be causing this stumble and black smoke???
1978 F-150 flareside. Primitive by todays standards but she was a jaw dropper back then. :-staun
1978 F-150 flareside. Primitive by todays standards but she was a jaw dropper back then. :-staun
Thread Starter
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Laughing Gas
Joined: Jul 2001
Posts: 849
Likes: 14
From: Fayetteville, NC
BLACK smoke??
[updated:LAST EDITED ON 27-Jun-02 AT 00:13 AM (EST)]>All,
>He said it's a new carb. Rejet!
>KingFisher
>P.S. Do it now before you wash out the rings and have to
>rebuild the bottom end.
I'm sorry...I don't quite follow that. What do you mean by wash the rings out
Ahhh..wait...now that I think about it I think I get it. You mean all the excess gas washing the oil off the piston rings and eventually getting onto the mains correct?
1978 F-150 flareside. Primitive by todays standards but she was a jaw dropper back then. :-staun
>He said it's a new carb. Rejet!
>KingFisher
>P.S. Do it now before you wash out the rings and have to
>rebuild the bottom end.
I'm sorry...I don't quite follow that. What do you mean by wash the rings out
Ahhh..wait...now that I think about it I think I get it. You mean all the excess gas washing the oil off the piston rings and eventually getting onto the mains correct?
1978 F-150 flareside. Primitive by todays standards but she was a jaw dropper back then. :-staun
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Cross-Country
Joined: May 2002
Posts: 98
Likes: 1
From: Southeastern Virginia
BLACK smoke??
Raw gas is a solvent, not a lubricant. If you're running really rich, the unburned gas dilutes the oil being applied to the piston rings, which is really bad. Too rich is either too much gas or not enough air. Patting the throttle activates the accelerator pump, which squirts gas directly into the throat. If the carb is new, it still needs to be set up for your truck. Most carbs have accelerator pump plus two or more circuits. Pilot jets meter during part throttle and main jets meter during full throttle. The pilot jet should have an air screw that will give some adjustment, but if the jetting is extremely off, it may have to be replaced with a different size. Main jets are usually just replaced. The only way to really dial the set up in is reading the plugs and driving the truck to note changes.
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