finally got everything fixed with the engine except the carb. What happens is that we turn on the truck and it turns over easily but then shuts off. It takes a while to get it going. at first if you give it gas it shuts off. It starts to putter and sound like its going to shut off. then you start to give it gas slow and all this black stuff comes out the exhaust. We do this for 10 to 15 minutes then it can run but we get no pickup at all. If we put it to the floor we get notin and it goes so slow. we have it set so it idles pretty fast but thats the only way we can keep the engine running when we drive. DO i just need to replace the carb or is it something else that i missed.
thankyou for you help.
joseph

 

Joseph, There must be a couple hundred things that can cause your problem. The black smoke is caused by unburned fuel. Either you have to much fuel going into the engine or the ignition system is not burning it. First things first, check the ignition system and ignition timing. Replace the carburetor only as the last option. Check for loose or leaking vacuum lines. Clogged air cleaner, loose carburetor, sticking choke. There's much more, and you may want to consult a mechanic before you start swapping out parts.
William in Atlanta

 

REMEMBER TO CHANGE YOUR SPARK PLUGS, WHEN IT BLOWS ALL THAT BLACK SMOKE YOUR WILL HAVE A VERY HARD TIME TRYING TO START YOUR TRUCK, BECAUSE NOW MOST LIKLEY YOUR PLUGS ARE ALL FOULED UP.

 

Joseph,

Sounds to me like a stuck needle & seat or bad float level.

Jim

 

I had a similar problem with my truck when I first got it. The gas tank had some trash in it that had made its way to the carb. The needle was stuck open allowing gas to flood into the engine. This caused my plugs to foul as was stated in another reply. Also, the spark plug wires were so bad that you could see a blue glow all around the distributor when you opened the hood at night. I cleaned out the carb, installed two filters in the gas line, one before the pump and one after. New plugs and plug wires and it ran pretty good.
1977 F-100
300 I-6 / C-4 (soon to be AOD)
Offy intake w/Edelbrock 500CFM
Hooker Ceramic coated headers w/duals
MSD6
Whiter whites/Brighter brights

 

>What
>happens is that we turn
>on the truck and it
>turns over easily but then
>shuts off.

Your choke might be out of adjustment. You might try setting to open sooner or later and see if that helps. It depends on your climate and time of year. Chokes should actually be fiddled with regularly, like every three months if you live somewhere with four seasons.

>It takes
>a while to get it
>going. at first if you
>give it gas it shuts
>off. It starts to putter
>and sound like its going
>to shut off. then you
>start to give it gas
>slow and all this black
>stuff comes out the exhaust.

Definitely sounds like your choke is goofed up. The black stuff is indeed unburnt gas. If the choke is on after the engine is warm, you'll be running rich, and when your acelerator pump/ power circuit comes on, there's even more gas going into the motor. Could still be a problem with your jets or rods. Might try getting some spray on carb cleaner and spritzing them (have to take top plate off your carb to do that depending on the type). If you're uncomfortable tearing into the carb, do the ignition work first. This is the most likely problem anyway.

> We do this for
>10 to 15 minutes then
>it can run but we
>get no pickup at all.
>If we put it to
>the floor we get notin
>and it goes so slow.
>we have it set so
>it idles pretty fast but
>thats the only way we
>can keep the engine running
>when we drive.

Check/adjust the timing to factory specs (remember to disconnect and plug the vaccuum advance when doing this). Make sure that the vacuum line for the distributor is routed properly. Someone on this site has a diagram available--look in the 351m/400 discussion. If there is no hint of the stock vacuum lines, route it from the carburetor and plug all other leaks.

>DO
>i just need to replace
>the carb or is it
>something else that i missed.
>

Sounds like the carb or ignition just needs a little help. Do the ignition work, and if that doesn't cure it, the carb needs adjusting. The difficulty in getting it to run when it is first started sounds to me like a problem with the choke, but everything else could be either carb or ignition--my hunch is that it's either timing, vacuum advance hose routing, or worn plugs/wires/cap/rotor or some combination of the above.

 

I had a similar problem with my 71'. I replaced almost the entire ignition system, fuel filter, even rebuilt the carb, but nothing helped. I eventualy gave up and and replaced the 25-30 year old holley and its ran like a dream ever since. I'm not saying "go out and blow $250 on a carb", but you might end up spending more if you replace parts left ands right and still end up buying a carb. Try and get someone to let you borrow a carb and see if it runs any better.