Hello, nice to meet ya, I'm new here. I will go introduce myself properly in a moment... but my question is more important right now.

I have a 1979 Straight 6 with a 1bbl carb and it idles like crap, it puffs out black smoke... running rich... but under acceleration and at speed it runs ok... ideas?

thanks in advance!
-grumman

I'll go introduce myself now

 

Hello, Grumman,

Mickman here, also new to the forum.

I would try to adjust the jet for the idle circuit; as I recall, there is an idle circuit and a high speed circuit in the carb. It's usually the air-fuel mixture screw on the side of the carb.

I have a '78 F-100 that has the same motor and carb, but it's got so many probs that I just consider myself lucky when I can fire it up and drive it.

Good luck.

 

Rebuilt carb is about $90, if I recall, and will run like new. If you can adjust the idle mixture OK, then fine. Otherwise, it's rebuild time.

 

I would also make sure the engine is at normal operating temp and the choke is not on when doing these adjustments.

 

I had replaced the needle and seat along with gaskets (cause it leaked fuel). everything looked ok, so I didn't do a complete rebuild, but it runs really bad... I've also posted this in the 300 I-6 forum... sorry for double posting, I didn't realize there was an appropriate area.

I tried adjusting the mixture screw while at "operating temperature" and it doesn't make a lick of difference.

I'm guessing the suggestion will be... rebuild it COMPLETELY or replace it.?

thanks for your replies!

heres the link to the other post so we can move to the right spot... https://www.ford-trucks.com/forums/6...-6-newbie.html

 

make sur your float level is set correctly. if its to high it will dump fuel in the engine and overload it at idle.

 

Before jumping the gun and buying a new carb, put a vacuum gauge on it and look for a vacuum leak first! I would also grab the carb and try to shake it. The things are famous for becoming loose and idleing like crap. If your carb is loose, you'll need to take it off to tighten the screws because they can only be accessed from the bottom of the carb!

 

I just had to replace the metal gasket under the housing that the egr valve is bolted to, mine was leaking. Made the engine idle very rough. I had tried everything else, but finally found this. Hope this helps.

Jeff

 

I appreciate the replies... I don't have vacuum guage so that is going to have to change soon.

the carb is tight, so no luck there.

I've replaced the gaskets and it doesn't leak anymore.

I adjusted the float acording to the directions that came with the kit... hopefully I did it correctly... It said that there should be an inch and a quarter droop... this is setting it dry... sound right? they even provided a nifty little ruler to use.

I noticed the exhaust manifold is cracked... how can this affect the way it runs... other than sounding like it has an exhaust leak?

thanks for your help!

PS I'm going to finish this in the other post, so as not to **** anyone off. thanks again for everyones input! you've been most helpfull!

 

i have a 78 with the same combo and it was doin the same thing. I had my buddy rebuild it and ive not had a single problem out of it the past 2 years. But with motorcraft carbs, either you got a good one or you dont no matter how many times you rebuild it.

 

The problem with buying rebuilt kits vs a rebuilt carb is that the rebuild kits don't come with new throttle shaft bushings.Rebuilt carbs do.

This is the main source of leaks.

 

my buddy has an 85 w/ 300 inline and a leaky exh. manifold. his backfires all the time after it shuts off. check the timing also. retarded can cause that and dieseling.

 

From my experiences when you buy a "rebuilt" carb for one of these trucks what it means is some company (maybe) put throttle shaft bushings in and then put a gasket kit in the carb without setting anything and ship them to the next store.

I went through three "remanufactured" carbs in as many days because all the ones I kept getting actually ran worse than the one i was replacing.

Finally on the 4th one before i even installed it on the truck I tore it down and set everything to spec. When I got it the float would hit the bottom of the float bowl and would touch the top of the airhorn before shutting fuel off (as in had i installed it, it never would have shut off the flow). the idle screw was also only in about 1/2 of a turn (no biggie), and the metering rod was run all the way down into the jet (as in it wouldn't have run over an idle had i installed it as is).

YMMV.

Justin

 

thanks for all the input guys... I've looked into it a little more and found that it could possibley be a vacuum problem as well... this is an old bread truck was in service for a long time and no telling what happend to it after they pulled it out of service... so, it seems I've got my work cut out for me. I intend to replace the exhaust manifold and rebuild the carb... see what happens and go from there... I'll keep y'all up to date as I go along! any other thoughts till then are welcomed and appreciated!

Oh, by the way... would any of you happen to know where I can find a diagram for the vacuum set up? I have no idea where everything is supposed to go so I can't even tell if its hooked up correctly now... thanks!

 

Get me the info off the sticker of the valve cover and Ill get you a diagram.

No Engine ID sticker ?

give me as much info about the truck as possible