Alright... I have an 83 F150 4x4 with a 351w and a C6. Motor was rebuilt and I just swaped in a new used transmission. I've tried to do some tuning on the carb but I haven't had much luck. First... When I try to cold start it dies right away and it does this a few times unti I hold down on the throttle. Then it wil fire up and run fine. Second... It dies when I shift it into gear.

I'm not sure if it's carb or vacuum leak. But any thoughts? It has a shiny Holley carb on it. I do have a second carb for the truck which is a Motorcraft manufactured by Holley. They look different from each other. I dont know if one would be better than the other.

 

I don't know how old you are or if you are familiar with carbureted engines so don't get too offended if I say something that may sound obvious to you.

To start a carbureted vehicle, you must first push the gas pedal down once or twice before starting to set the choke. This will shoot gas down the intake and close the choke plate on the carburetor so that a richer air/fuel mixture will be provided to keep the cold engine from stalling. When the engine fires up, the fast idle cam will be activated which will make the truck idle higher to keep the truck from stalling. After the truck idles for a minute or two on high idle, you push the gas pedal down again to drop the fast idle cam which will also lower the idle down. As the engine warms up, the choke plate will gradually open up to run on a leaner mixture. If you don't drive it for a few days, you may need to push the gas down a few times before starting the engine.

Is the choke hooked up?

 

Yes it is.

 

Alright. Is the choke plate closed when you push the gas pedal down before starting?

 

Yes. The choke plate is closed when its started and as it warms up it slowly opens.

 

OK. With your truck turned OFF, take off the air cleaner and look down the throat of the carburetor while you manually open the throttle.

Do you see two strong streams of fuel shoot out or does it dribble out?

 

There are two strong steady streams.

 

You got me, Chief.

I would have to actually see and hear the truck to suggest something else. In my experience, Holley's are much more fickle than the Ford carburetors, and that is why I tossed a nearly new Holley Street Avenger for an Autolite 4100.

Maybe someone else will come along and have another suggestion.

 

It sounds like everything is working correctly, but the choke may be opening up to quickly. Is this a Holley 2bbl carb? It has the large round black piece on the pass side correct? If so, then loosen the black plastic piece, and turn it toward the richer direction(some of them are labeled "richer" and "leaner" with arrows). If it's not labeled, hold the throttle wide open(with the engine off) while you turn the black piece, and you will see what makes the choke close more or less.

 

Thanks Franklin! I completely forgot about the choke cap adjustment. That sounds like his problem.

Listen to Franklin, Condor945. I have learned most of what I know about carburetors and chokes from him.

 

It is a 4bbl, but I will try adjusting the choke tomorrow and see how that changes things.

I appreciate the responses and your time. I'll let you know what happens.

 

Lariat or Franklin... Are you able to share what your RPM's are at the fast idle, regular idle, and in drive/reverse.

I played with the choke a little, but that didn't seem to help much. To me it seems like my RPM's are all off.

When I starts it idles around 1,100-1,200 but it doesn't seem to go any higher or lower unless I shift it into gear. When it goes into gear sometimes it dies, sometimes it'll run, around 600 RPM's.

Also... The carb is a Holley 4160. The previous owner must've put that on there since the stock Holley's were 4180C.

 

It'll usually say on your under-hood emissions label on the radiator support what your various idle speeds are. It should have listings for fast idle and the idle speed when in park as well as curb idle when in drive.

It sounds like your idle in Park is too high compared to your idle in drive. Your idle in park should be around 800 rpm and your curb idle when you put it into drive should be about 600. Check your emissions label for your fast idle speed when warming up. Also, check to make sure your choke is wired up right and that its adjusted correctly, as well as all the linkages present.

When you shift the truck from park to drive, does the transmission make a loud clunking noise?

 

When you start it, the choke should be shut. If the choke is shut, the idle should be very high, and as it runs will get higher and higher till you pat the gas pedal to the floor, and that will kick the idle down a little bit. When it gets fully warmed up and the choke is completely straight up and down, the throttle will be resting against the idle adjustment screw on the driver's side of the carb.

All the other times when the choke is active, the throttle will not be against the idle adjustment on the driver's side, it will be against the "fast idle" adjustment that is on the pass side of the carb.

There is a cam that is hooked to the choke linkage located on the pass side of the carb. When the choke is active, this cam comes around, and the fast idle adjustment screw hits this cam, and it makes the engine fast idle when the choke is active, this helps the engine warm up and keeps it from stalling when it's cold. The cam has somewhat of a curve, so more choke means a faster idle. The choke spring located inside the round black piece is usually not strong enough to move everything mechanically by itself, that's why you have to "kick" the gas pedal once in awhile to let the choke and the fast idle cam relax to a new position. This is the same reason why you should kick or floor the gas pedal a couple of times before you start it on a cold morning, so the choke can close and the cam can come around and set the fast idle. It's not strong enough to do this without you hitting the gas pedal first to let it set.

 

What type of choke does the 4160 Holley have? The 4180 that came on the truck
has an electric choke that gets its power from the alternator which is 7 volts. The 4160,
if it has an electric choke, will most likely need 12 volts to operate properly. You might
want to verify which you have.