Carb Question
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Carb Question
I have a '66 F100 with a 390 V8.
The carb i'm running is a 0-6619-1 4160 600cfm
I have both mixture screws at only 2 full turns out, but it runs really rich.
The truck is running good, but there's blue-ish smoke coming out end of exaust pipes.
What can I do to correct this problem?
~Bob
The carb i'm running is a 0-6619-1 4160 600cfm
I have both mixture screws at only 2 full turns out, but it runs really rich.
The truck is running good, but there's blue-ish smoke coming out end of exaust pipes.
What can I do to correct this problem?
~Bob
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Joined: Feb 2010
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From: Atlanta
I think I would check the float adjustment first, start the truck and carefully remove the float level sight plug on the side of the primary bowl, I put a rag under to catch any fuel that might spill out, the fuel level in the bowl should be even with the bottom of the sight plug, otherwise adjust the float level adjusting screw on top of the bowl, good to have a lot of light and good eyes as everything is vibrating and it's a little dicey letting fuel run out of your carb onto a hot manifold. Tighten the float level lock nut, reinstall the sight plug and repeat this procedure for the secondary bowl.
Once the fuel levels are set in both bowls, the best way to adjust the idle mixture needles is with a vacuum gage, start at 1 1/2 turns out and move each screw 1/8 of a turn at a time (make sure you do the same to each screw) until you have the highest vacuum reading, some folks can do this by ear but I'm not that sharp so I use the vacuum gauge and reset the curb idle screw with a tach, that should get you pretty close unless there's something else going on with the engine or carb.
Once the fuel levels are set in both bowls, the best way to adjust the idle mixture needles is with a vacuum gage, start at 1 1/2 turns out and move each screw 1/8 of a turn at a time (make sure you do the same to each screw) until you have the highest vacuum reading, some folks can do this by ear but I'm not that sharp so I use the vacuum gauge and reset the curb idle screw with a tach, that should get you pretty close unless there's something else going on with the engine or carb.
Posting Guru
Joined: Dec 2010
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From: Chino Hills
The Carb you listed is a smogger carb, but from what I could offline quickly says it runs lean.
My guess is that somethings a miss on the inside, and allowing extra fuel by the jet plates.
Although are you sure it is not burniong oil? Is the timing set right, points bad, or coil weak? Just wanna dot a couple of I's before you rush off to spend money you may not have too now.
So if it is the carb my remedy would be atleast to re-build the carb with a quality kit.
Myself I would buy the parts nessacary to improve the one you do have. You can add 4 corner jets, dual fuel inlets, quick change vac spring, and a re-build kit for less then a new carb. With a good carb base you can build yourself a trick carb for less then a new one by alot.
That or buy a better 600-750cfm vac secondary holley carb or equivalent.
My guess is that somethings a miss on the inside, and allowing extra fuel by the jet plates.
Although are you sure it is not burniong oil? Is the timing set right, points bad, or coil weak? Just wanna dot a couple of I's before you rush off to spend money you may not have too now.
So if it is the carb my remedy would be atleast to re-build the carb with a quality kit.
Myself I would buy the parts nessacary to improve the one you do have. You can add 4 corner jets, dual fuel inlets, quick change vac spring, and a re-build kit for less then a new carb. With a good carb base you can build yourself a trick carb for less then a new one by alot.
That or buy a better 600-750cfm vac secondary holley carb or equivalent.
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I should have mentioned that I did already check the float level, and that is good.
I do not have a vacuum gauge, so maybe it's time to buy one.
As for if the truck burns oil. I don't think so because my oil level never goes down, I should say, I never have to add oil before oil changes. The exhaust is a very strong-gassy smell with a slight blue-ish tint, not really "smokey", so to speak.
The fact that it's running fine, I guess I didn't think the timing, points, or a weak coil would be my issue. But it wouldn't be the first (or last) time I've been wrong
I've never taken apart a carb, and only know the basics...idle, float setting, mixture screws.
Thanks for the replies.
~Bob
I do not have a vacuum gauge, so maybe it's time to buy one.
As for if the truck burns oil. I don't think so because my oil level never goes down, I should say, I never have to add oil before oil changes. The exhaust is a very strong-gassy smell with a slight blue-ish tint, not really "smokey", so to speak.
The fact that it's running fine, I guess I didn't think the timing, points, or a weak coil would be my issue. But it wouldn't be the first (or last) time I've been wrong
I've never taken apart a carb, and only know the basics...idle, float setting, mixture screws.
Thanks for the replies.
~Bob
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Oh yeah...I read that if you turn the mixture screws all the way in the engine should die, but it didn't. Of course I didn't move them at the same time, but it seamed odd to me that it didn't sound that much different when turned in all the way. Maybe this is because of the smog-type carb it is and running leaner. I don't know, but wanted to mention that in case it helps.
Thanks again,
~Bob
Thanks again,
~Bob
Postmaster
Joined: Nov 2002
Posts: 3,447
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From: Littleton, CO
Blue smoke is an indication of oil burn
Black smoke is an indication of a rich fuel mix
White smoke is an indication of water/coolant in the combustion chambers
--Mike
Black smoke is an indication of a rich fuel mix
White smoke is an indication of water/coolant in the combustion chambers
--Mike
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Elder User
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From: Fairbanks
If you can turn the screws all the way in and the engine does not stumble the throttle is usually open to far and you are bypassing the idle circuit.
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Can anything be done about burning oil?
Like I said, I never have to add any oil between oil changes ???
As far as the "throttle being too open, again how do I fix that. I don't really understand how a throttle can be too open. It's not like the the throttle cable is holding it partially open from the start. Please help me understand.
Thanks, Bob
Like I said, I never have to add any oil between oil changes ???
As far as the "throttle being too open, again how do I fix that. I don't really understand how a throttle can be too open. It's not like the the throttle cable is holding it partially open from the start. Please help me understand.
Thanks, Bob
Senior User
Joined: Jan 2010
Posts: 398
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From: AR
Something I have seen before is very slow ignition timing (which would close slow idle) being made up for by setting idle screw to hold the plates too far open.
Elder User
Joined: Apr 2008
Posts: 619
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From: Montpelier, VA
The two screws on the front of the carb are for adjusting the idle mixture. They have nothing to do with the fuel mixture as the truck is driving down the road. As was mentioned previously, blue smoke indicates oil burning and black smoke is indicative of a rich mixture.
Laughing Gas
Joined: Aug 2010
Posts: 979
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From: Colorado Springs CO
Some Holleys use a reverse idle mixture circuit-I can't remember if yours is one of 'em. In other words, turning the screws in makes it richer, & backing it out makes it leaner. Might try that & see if it helps.
However, as posted above, the mixture screws only control idle-once you give it a little throttle, you're out of the idle circuit.
However, as posted above, the mixture screws only control idle-once you give it a little throttle, you're out of the idle circuit.
Postmaster
Joined: Nov 2002
Posts: 3,447
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From: Littleton, CO
To set a carb, you should start at 1 1/2 to 2 turns out on both screws, set the idle at 600 rpm, then adjust from there. I do 1/2 turn at a time in, back and forth across the screws, until it slows the idle, then tweak from there. A vacuum guage makes it easier. If you still have black smoke when you hit the pedal while you are running, you need to lean down the jet size. Blue smoke could be bad valve seals or rings..., there is no quick fix usually, but it is just a trace that causes the smoke so you may not consume oil between changes..
Thats my $.02's --Mike
