i posted this in the fuel forum but no response https://www.ford-trucks.com/forums/s...84#post2388384

 

What carb is it?? 600, 750?
Something is not right if you need choke closed to keep it running, but plugs are black.

If you open choke completely, but hold throttle open slightly, will it run??
Does it look like lots of fuel being run out of boosters at idle? you should not really see much other than a light mist.

I'm thinking maybe the fact that the choke closing is also opening throttle plates(it should in fact). With the mix of these two things is allowing enough air to mix with excess fuel. Kinda a catch 22.

Power valve could be bad, allowing excess fuel to be drawn into engine, but the throttle blades should have to be open far enough for it to draw. If you look at bottom of carb(at blades) you will notice a couple of slots. The bottom one is idle circuit(what it should be idling on), the next is transfer slot which helps blend between idle and main metering. The main metering feeds fuel thru the boosters.

 

yes it does run when i take the choke off and hold the idle i tried rebuilding the carb to solve this but no effect the carb is only a few monthes old it is a 600cfm manual choke carb 4160

 

Hmmmm. So this did this from brand new? You bought it new, or from someone else that said is was "new". Was it never installed before you got it?
Manual choke??
Have you re-checked the float levels?
Can you see large amounts of gas dribble from the venturi boosters when it's "idling".

The bad thing about the choke set ups on these, is it has to close the flap much more than upping the idle. I usually find that I have to adjust the high idle HIGHER so that it can actually idle fast enough. Most of the time I remove the choke plate and only use the high idle function. I crank the high idle screw up til I get 1400 rpm or so. Usually if the choke flap is still on,it is closed by that rpm and then floods the engine.

 

the gas is just at the bottom of the hole when you remove the screws when i got the carb it had about 100 miles on it then sat for a few weeks then i bought it it ran great till all of a suudden two weeks ago when it started doing this so i rebuilt it and it still does it could there be something clogged

 

this is what holley said to me.what is the lash he talks about

Hello

You did not state that you tuned the catb to your application. The first thing
that you need to do is adjust your float level, no fuel should run out the sight
plug with the engine running. and check to make sure that your fuel pressure is
not over 7 PSI. I suggest 6-6.5 PSI Make sure the acc. pump is properly
adjusted. It should be at zero lash at idle. and have at least .015" gap at Wide
open throttle with the pump lever pushed all the way down. Then try turning in
the idle air screws all the way in with the engine running.
If the engine continues to run with both screws all the way in, then the carb is
letting fuel into the engine from someplace other than the idle
circuit. We have to find out where from and correct it (with the screws all the
way in the engine should die) Next you want to check the manifold
vacuum with the engine idling in gear. This will tell you which size power valve
to use. If your vacuum is 9" and under divide by two, and that is the size you
need. If it is 10" and over use a 6.5 PV. You may have to replace it with the
correct size. If you get all of this corrected and the engine still runs rich
then you will probably have to remove the carb and adjust the secondary throttle
plates open to the bottom of the transfer slots. This will allow you to close
the primary plates down some. If either plates are open too far then fuel will
be pulled in to the engine from the transfer slots in the base plate. By
adjusting those plates like I said, the carb will get the same amount of air at
idle, but it will get it evenly from the
front and rear instead of just the front. Once you get it so the engine dies
with the idle air screws, then you can continue with the rest if the
adjustments. Next you need to adjust the idle air screws. Turn them in until
they seat lightly then back them out 1.5 turns. Start the engine and
let it warm up. Hook up the vacuum gauge to manifold vacuum. Check it at idle in
gear. Adjust the idle air screws evenly until you get max vacuum
(the vacuum will drop off if you go to rich or lean) With that done you can
start working with your jetting Unfortunately I can't tell you how to jet it.
Each engine is different and has different requirements. It is a trial and error
process. Start with the stock jetting and go from there, Run the engine under a
load and read the spark plug color to find out which way you need to go. Black
is rich and white is lean. It is best to tune the primaries first at part
throttle and the secondary's at WOT run the vehicle at least a quarter mile and
shut it down under throttle in order to get an accurate plug reading. This
should be accomplished on a track or a long stretch of road with a wide shoulder
that it can be done safely.Adjust it until you get a nice light brown color on
the porcelain of the plug. when you get this adjusted . If you have a off line
hesitation that is less than a second Increase the shooter by one size. If it is
over a second increase the shooter by Two. If it makes the hesitation better you
can increase accordingly if it gets worse drop the size.
Thanks Tom

 

The accel pump and the lever that actuates it. There needs to be a certain clearance betweeen the accel ARM and the lever(spring loaded bolt presses down on it). Basically when throttle is closed, it should just be slack(not pushing down on arm). That way when at idle, the arm is not trying to pump fuel. Then when at WOT, there needs to be cushion so that the accel pump is not wedged tight. The reason for the spring on the bolt.

The plugged scenario seems unlikely, but who knows. Most functions require air to drawn fuel into the venturi. If a channel was plugged, it would seem that it would not run do to lean condition.