Hey y'all, absolutly the first time trying this so help, advice, critisims greatly appreciated...
Question...went out and bought a brand spanking new carter afb 625cfm emission ready electric choke for my 79 f250 460...cannot smooth out the idle...it shudders, stutters and fluctuates...
I set everything up the same as the old carb (also a 625 afb), floats, rods and jets etc...good fuel flow to carb, tune-up recent etc
would an faulty egr cause this problem? egr seems a little tight when depressed and idle stalls so it would appear to be functioning. the mixture screws are turn out about 3 1/2 turns rich just to make it idle bearably.
runs fine down the road, good acceleration and passing gear kicks in when needed it just doesnt idle right in park or drive while stopped in traffic...thanks

 

I would look for a vacuum leak somewhere. My Edelbrock works great.
Did you plug the threaded hole in the rear of the carb?

 

Thanks for the reply...
Roger that on the cap screw at the back on the carb...first thing I installed..
I concur about the brand of carb...however, I didnt have this much trouble when I installed the first one...
Well finally got the thing to idle passebly, It no longer feels like its about to fall apart, yet still not as smooth as its should be...
I thought maybe the floats were off...reset at 9/16=inverted
2"= upright
books says...7/16=inverted
1 1/4 (+\-) 1/4
Mixture screws still at 3 1/2 turns rich...
Now Im getting a little dribble of fuel down from the top looking into the throat, while idling (didnt do this before)would indicate slight flooding(?)...
Fuel level in bowl is slightly below the u-shaped seperator...
Yet,
the idle is passeble, better than before anyway...
I will go back over all seal, gaskets, lines to recheck for vacuum leak for the 4x...

 

Hi,

Do you have a vacuum gauge you can hook up? Look at what it is doing at idle. Should be around 16-22 inches and steady.

It can tell you alot about what is going on.

If you need more help let me know.

-Brents

 

3 1/2 turns out is waaaaay rich!

You should be in the area of 1.5 to 2.5 turns out.

My first question is why are you replacing an AFB with an AFB?

What was wrong with the first one?

Make sure all base gaskets are new, even the EGR gasket when switching things out. Sometimes you can reuse sometimes ya can't.

Do you have the bowl vent plugged or connected to something?

Are you running the distributor off of the left side port? If you aren't you should be.

Is the other port plugged or connected to something?

Josh

 

spary a little starting fluid around under carb and intake area at idle if it evens out, you got it. But be carefull of flames make sure no spark plug wires are arching 1st.GOD BLESS

 

If there is fuel dripping down the carb at an idle, then something is wrong. You may want to pull the top again and remove the needle and seats to see if there may be a small piece of debris in one of them keeping it from shutting off all of the way. It could be a small piece of rubber fuel line from when you installed the carb.

 

[updated:LAST EDITED ON 24-Nov-02 AT 09:39 AM (EST)]Thanks for all the input...
Since I had done everything I could think of, I went back to the beginning, lxman said vacuum and guess what?? found it under the EGR plate...Hmmm...seems I remember going through this whole thing when I put the first one three years ago...How come I never take notes when I do these little (1)day projects that end up taking 2 weeks...guess cuz that would make sense...waiting on egr gasket now.
AFB for a AFB....the first one was very old, spitting and pukin from everywhere it's not supposed to...been rebuilt untold many times questionable history...found a brand new one at Lopers's 249.00 out the door, overtime money was burning a hole in myn pocket, plus it sure is pretty sitting in that dirty ole engine compartment
Well, since I had a little time on my hands waiting for the gaskets to come in...I caught on some of those little annoying things; dash lights fixed (some emorycloth, pencil eraser), replace any rubber fuel lines and added another in-line filter between pump/tank, gas down here is very dirty from what Ive seen...Ive reset the carb back to spec...7/16 inverted level, 1 1/4 drop level, jet/rod combo .092 an 16-98 respectivly (gets me past emmissions)Now if only that dang gasket would get here...2.5 days waiting so far...

 

Nope...no vacuum gauge, my next purchase for sure though!
OK, Ive replace ALL gaskets, made sure everything was snug down tight, sprayed down all the gasket seals with no change in idle (had a slight change before, seem better now)reset the floats to carter reccomendations, recheck for leaks and now it appears that Im getting excessive fuel from the venturis.....
So, I was getting less fuel through the venturis at Idle when my float drop was at 2" than at the current 1 1/2....strong gas smell, obviously Im getting to much gas(?)...There are two different measurements for the floats...Im soooo confused..
Clean and /or replaced all fuel lines and filters (see thru filters)seems clear of debris with good flow....
If I had a cliff I'd drive ole betsy off of it and stick to the harley....
PS...thanks for the input....

 

Thanks man, see my latest post for the update....Im still stump...