SBC issue.

[GM-power]

While im driving and the engine is running fine then all of a sudden its sputtering and losing power, not stalling but it has twice after the above symptoms. The engine is rebuilt but the carb was the one on it before. Could it need adjustment? I figure the timing is alright cause it runs fine most of the time. I know the details aren't that clear, but help is much appreciated.
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[86c20]

my monte carlo did this to and then the filter in the carb pluged up

[motornut]

whenit's warm /cold?
hows your sending unit?
vacume leaks?
vacume advance?

[notyo_cheez]

Originally Posted by GM-power

While im driving and the engine is running fine then all of a sudden its sputtering and losing power, not stalling but it has twice after the above symptoms. The engine is rebuilt but the carb was the one on it before. Could it need adjustment? I figure the timing is alright cause it runs fine most of the time. I know the details aren't that clear, but help is much appreciated.
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My $0.02, sounds fuel related. Check your fuel filter, cheap and easy stuff first. Take it out and blow through it, if you can't replace it.

You might have debris in the fuel tank, fuel pump heading south, or both. Once those are ruled out check out the carburetor, if it's really old look at a rebuild.

Just a guess since I can't look at it.

[Axle]

I've had similar happen a couple times. Dirty fuel getting filters plugged, and once the charcoal canister letting go. Found little black specs in the carb, plugged the line from the charcol cannister and thats the end of that problem.

Alex.

[mopar346]

How long were you driving when it occurred? How did it run after you let it sit and cooled off? What exhaust are you running? Still got the factory cat? What ignition are oyu running? With limited info it is hard to say what the culprit is.

Carb
Fuel filter
Fuel pump
Ignition module
Cat

And even some other more obscure posibilities.

[GM-power]

Well I took it to the family mechanic he said the carb has debris in it so we ran it floored it and its fine now. I am pretty sure the carb is on its last leg and he confirmed. Im going to check the fuel filter. Thanks for the help guys.
@mopar346 it was happening at all distances but not the woke ride. The muffler fell off so I got open pipe under the truck, and its heavy-half so no cats
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[mopar346]

Well, sounds like you found it. Make sure he figures out where the debris is coming from.

[GM-power]

He and I are going to look over the truck front to back sometime soon. I don't know what carb is on it now but it is going to need some work or replacement soon.
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[GM-power]

Well it happens again! On the interstate. There is construction going on so there was no shoulder. I accidentally stalled it. Wouldn't start. The flap on top of the float is sticking, and I seem to only have it happen a little bit after I put some gas in it. Its a quadrajet. Would a new carb be better? I don't hear high praises of the Q-jet; so im thinking about a new carb. Thoughts or ideas, guys?
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[rcbildr]

You will get better power and economy with a properly built/rebuilt q-jet.

[GM-power]

I don't have problem getting a edelbrock or holley carb. I drive this thing daily so I don't want to deal with this crap all the time. I am almost Leary of keeping this Q-jet.
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[mopar346]

Q-jets are great carbs when right, the reason they get a bad wrap is once they do have problems most people don't know how to fix them. Chances are if you get the PROPER kit, boil it out properly and build it by the instruction it will be fine. Small primaries offer good gas mileage and the massive secondaries (depending on which one you have) provide plenty of power for 99% of the applications out there. And you gotta admit the sound when the secondaries kick in is awesome. A Holley is easier to work on and more tuneable for the commoner, Edelbrocks put lightly suck in my opinion and I'm a Mopar guys (they are based on the old Carter AVS many of myt beloved Mopars came with). I would invest the time in building the Q-jet, but if it is debris again then it will happen again regardless what carb you have. Make sure you have a good filter and have the tank boils out and lined if need be.

You mentioned a flap on top of the float, are you talking about the choke flap over the primaries? If that is what has cloesd off and shut you down then you have a choke linkage issue not a carb problem. To test the theory remove the choke flap by removing the 2 screw (be very careful not to drop them in the carb) and run a few days without it.

[GM-power]

I highly doubt debris was the culprit this time. I had some dad move the flap when I cranked it. It fired right up. So it could be a choke issue. This sputtering happens occasionally, but I have a theory that it only happens miles down the road after I put gas in the tank. I don't even fill it up all the way. When it isn't sputtering the motor is real smooth and it will go!
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[mopar346]

It doesn't really sound like a carb problem, might be in some of the stuff around it, ie choke, fuel pump, filter, even vapor lock (how hot is it there while your driving/). You need to find you a good old guy that remembers carbs and have them look at it.

[GM-power]

A good friend of mine who's pretty mechanically inclined look at it with me. We check all the vacuum lines and the fuel line, and choke. We also checked the filter. Im going to get a filter soon cause it was dirty. The carb is fine. I just have to pin point the problem.
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[Axle]

Originally Posted by GM-power

Well I took it to the family mechanic he said the carb has debris in it so we ran it floored it and its fine now. I am pretty sure the carb is on its last leg and he confirmed. Im going to check the fuel filter. Thanks for the help guys.

What does "ran it floored it and its fine now" supposed to mean?

If you/he did not remove the airhorn off the carb, remove the screw and checkball under the accelerator pump, pull out the metering rod/valve and spray the passages clean, you still have a good chance of dirt being in those passages, and as that dirt gets moved around from the vehicle shaking or the fuel moving, the dirt eventually will stop up a passage and things will run bad. If you are lucky, it clears itself up, if not, it runs bad for a while until enough shaking and vibration has moved the debris so fuel can flow again.

Alex.

[GM-power]

Changed the fuel filter and check all the vacuum lines. It runs real smooth. Hopefully its problem solved!
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[INSIDIOUS '86]

Originally Posted by rcbildr

You will get better power and economy with a properly built/rebuilt q-jet.

Better power should be crossed out
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[mopar346]

If he has one that is not working correctly and he gets it rebuilt properly then it provide better power.

Q-jets wont give BG power but it will provide very respectable performance and if you source the right one you can get some serious CFM out of them. In many cases a properly working Q-jet will out perform the smallish Holley people replace them with on the cheap and virtually any Edelbrock made.

[INSIDIOUS '86]

Originally Posted by mopar346

If he has one that is not working correctly and he gets it rebuilt properly then it provide better power.

Q-jets wont give BG power but it will provide very respectable performance and if you source the right one you can get some serious CFM out of them. In many cases a properly working Q-jet will out perform the smallish Holley people replace them with on the cheap and virtually any Edelbrock made.

All true. Most q jets are big as well. Still a pita most of the time.
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[GM-power]

I will admit opening the secondaries on the Q-jet is alot of fun!
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