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4300/4350 carb help

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Old 02-12-2012, 08:35 AM
miottimouse
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4300/4350 carb help

good day i just bought another truck on the weekend [now have 8] 79 f250 lariat with 460 engine this truck was sitting for about 2 years we had to replace the fuel pump/carb fuel filter and added another filter between the frame fuel line/fuel pump just to be sure filled the tank with fresh fuel/added gas treatment and drove her home so far i went through 3 tanks of gas/the filters still clean so i know the fuel tank/gas is good but i get a hesitation when i put my foot in to it so it has to be very gentle or it bogs idles/starts fine wide open is good but i am thinking the main circut is plugged my ? is does any one know where to find these motorcraft carbs either rebuilt or kits to rebuild? i have not checked closly but i am thinking its a spread bore and since this truck/engine was bought to replace the 400 in my bronco i would like to just re&re with out changing the intake if i cant find any thing to use and have to change the intake then i will use a square bore carb [holly/eddy ect] i will check tonight and see if i can find any tags/#s ect thanks for your help
 
  #2  
Old 02-12-2012, 08:57 AM
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My guess is that it's your accelerator pump. Look down the carb throat and move the lever to full throttle. You should see two solid streams of fuel.

Here is some info for you. Basically what you will find in a carb rebuild kit.


Autolite/Motorcraft 4300 and 4350 4-BBL Carburetors



Print
DESCRIPTION



See Figure 1




Fig. Fig. 1: Exploded view of the Motorcraft 4350 carburetor components

The model 4300 and 4350 4-barrel carburetors are composed of three main assemblies: the air horn, the main body, and the throttle body. The air horn assembly serves as the fuel bowl cover as well as the housing for the choke valve and shaft. It contains the accelerator pump linkage, fuel inlet seat, float and lever, booster venturi, and internal fuel bowl vents.
The main body houses the fuel metering passages, accelerator pump mechanism, and the power valve.
The throttle body contains the primary and secondary throttle valve and shafts, the curb idle adjusting screw, the fast idle adjusting screw, the idle mixture adjusting screws, and the automatic choke assembly. It is used on V8 engines.
ADJUSTMENTS - Float



4300 MODEL
See Figures 2 and 3




Fig. Fig. 2: Adjusting the float level on the Motorcraft 4300 and 4350 carburetors





Fig. Fig. 3: Fabricate float gauge bending tools by following the illustrationMotorcraft 4300 and 4350 carburetors

  1. Adjustments to the fuel level are best made with the carburetor removed from the engine and the carburetor cleaned upon disassembly.
  2. Invert the air horn assembly and remove the gasket from the surface.
  3. Use a T-scale to measure the distance from the float to the air horn casting. Position the scale horizontally over the flat surface of both floats at the free ends and parallel to the air horn casting. Hold the lower end of the vertical scale in full contact with the smooth surface of the air horn.


The end of the vertical scale must not come into contact with any gasket sealing ridges while measuring the float level.
  1. The free end of each float should just touch the horizontal scale, if one float is lower than the other; twist the float and lever assembly slightly to correct.
  2. Adjust the float level by bending the tab which contact the needle and seat assembly.


4350 MODEL
  1. Invert the air horn assembly and remove the gasket.
  2. Measure the distance from the floats to the air horn rim using a T-scale. Position the horizontal scale over the flat surface of both floats at the free ends, parallel to the air horn casting. Hold the lower end of the vertical scale in full contact with the smooth area of the casting, midway between the main discharge nozzles.


Do not allow the end of the vertical scale to contact any gasket sealing ridge while measuring the float setting.
  1. The free end of the floats should just touch the horizontal scale. Float-to-air horn casting distance should be <sup>29</sup> / <sub>64</sub> in. (11.5mm). Bend the vertical tab on the float arm to adjust the distance.


Initial Choke Valve Clearance
  1. Remove the choke thermostatic spring housing.
  2. Bend a wire gauge (0.035 in. [0.89mm] diameter) at a 90 angle about 1.8 in. (45.7mm) from one end.
  3. Block the throttle open so that the fast idle screw does not contact the fast idle cam.
  4. Insert the bend end of the wire gauge between the lower edge of the piston slot and the upped edge of the righthand slot in the choke housing.
  5. Pull the choke piston lever counterclockwise until the gauge is snug in the piston slot. Hold the wire in place by exerting light pressure in a rearward direction on the choke piston lever. Check the distance from the lower edge of the choke valve to the air horn wall.
  6. Adjustment is done by loosening the hex head screw (left-hand thread) on the choke valve shaft and rotating the choke shaft.


Fast Idle Cam
4300 MODEL
  1. Loosen the screws on the choke thermostatic spring cover and rotate the housing <sup>1</sup> / <sub>4</sub> turn counterclockwise. Tighten the screws.
  2. Open the throttle and allow the choke valve to close completely.
  3. Push down on the fast idle cam counterweight until the fast idle screw is in contact with the second step of the cam and against the high step.
  4. Measure the clearance between the lower edge of the choke valve and the air horn wall.
  5. Adjust the turning the fast idle cam adjusting screw.
  6. Return the housing to its original position.


4350 MODEL
  1. Run the engine to normal operating temperature. Connect an accurate tachometer to the engine.
  2. Disconnect and plug the EGR and TCS vacuum lines.
  3. Position the fast idle screw against the first step of the fast idle screw. Adjust the fast idle screw to give a reading of 1600 rpm.
  4. Return the linkage to its normal position, unplug and reconnect the vacuum lines.


Choke Unloader (Dechoke)
  1. Open the throttle fully and hold it in this position.
  2. Rotate the choke valve toward the closed position.
  3. Check the clearance between the lower edge of the choke valve and the air horn wall.
  4. Adjust by bending the unloader tang on the fast idle speed lever toward the cam to increase the clearance and away to decrease the clearance.


Do not bend the unloader tang down from the horizontal. After adjustment, there should be at least 0.070 in. (1.78mm) clearance from the choke housing with the throttle fully open.
Accelerator Pump Stroke
The accelerator pump should not need adjustment as its stroke is preset in compliance with exhaust emission control standards. If for any reason the stroke must be altered, it may be done by repositioning the link in the desired holes.
Fast Idle Speed
The fast idle speed is adjusted with the engine at operating temperature and the fast idle screw on the second step of the fast idle cam. Adjust by turning the fast idle screw in or out as required.
To adjust the fast idle speed, you must plug the EGR valve vacuum line and disconnect the TCS solenoid wire.
Dashpot
Some carburetors are equipped with a dashpot to prevent stalling. The dashpot adjustment procedure for these carburetors is as follows:
  1. Be sure that the throttle valves are closed tightly and that the diaphragm stem is fully depressed.
  2. Measure the clearance between the dashpot stem and the throttle lever with a feeler gauge. For the proper clearance specification, see the chart.
  3. If the clearance is not correct, adjust it by loosening the locknut and rotating the dashpot until the proper clearance is obtained. Tighten the locknut.
.
 
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Old 02-12-2012, 09:12 PM
miottimouse
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thanks for the info but yes the acc pump is working fine lots of fuel in the squirters seems to be the main circut and it is a spread-bore could you do me a real big faver? and check priceing for a rebuilt carb and the rebuild kit? as it wont let me in with a canadian postal code the part numbers on the tag are
d7te csa a-8c-21 thank you regurds joe
 
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Old 02-12-2012, 09:39 PM
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OldStyle
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Just for referance only a carb kit is 30.00.
Walker Products 15591D - Carburetor Kit | O'Reilly Auto Parts

A rebuilt carb looks to be just over 300.

I would get a carb kit myself or you could find a re-builder in your area; keeping the carb that came with your truck. It's already jetted correctly and will, properly rebuilt, give you years of service.

If you go with a re-builder take a pic of the tag, put your own marks on the carb body, and let them know you want your own carb back.

.
 
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Old 02-12-2012, 09:51 PM
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the carb kit for mine was 20 dollars or so, i just pulled the top of the carb off still on the truck and cleaned it out real good replaced my accelerator pump and jets and needle/seats in just a few minutes.

the kit i bought from oreilly auto parts made by walker,

lmctruck offers a carb i seen for under 300 bucks too
 
  #6  
Old 02-12-2012, 10:45 PM
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I recently bought a carb kit from oreilly's auto parts and paid $30 bucks with it . I had my older brother do the carb kit (he can do these carb kits with his eyes closed) and after doing the carb kit it seems to run pretty good . I also notice when I floor the peddle it also hesitates and i gotta lay off the pedal a bit too in order for it to really take off...
 
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Old 02-16-2012, 08:34 AM
miottimouse
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thanks guys serched the net long enough i found a rebuild kit for $20.00+ $8.00 shipping to canada so i will try my hand and see how it turns out if it dosnt work i can all so swap intakes
 
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Old 07-26-2012, 06:28 PM
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4300 and 4350

I have 1974 Ford F350 with a 460. I either have a 4300 or 4350 I don't know. The tag on the carb says D4TE CA. Anyway, I want to replace it with a Edelbrock carb. What I need to know is what is 'CFM' for the 4300 and the 4350. Please can someone let me know. Either post or email [email protected] Thank-you, Ric
 
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Old 07-27-2012, 06:44 AM
miottimouse
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a carb aprox 600 cfm will work well with your 460 thats what i run on all of mine and i assume both the 4300s would be close to that
 
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Old 01-01-2014, 03:55 PM
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rawiron81, my 77 f-250 is doing the same thing so I think the rebuild kit is the way to go. Also my truck has all the CA emission parts as it is still required to be smogged there, however, I recently moved to Idaho would really like to remove all the emissions stuff, but I'm not sure with the carb I have what lines would need to be plugged and if the EGR valve has to be retained and if I need to get a nonvacuum type distributor once I remove all the vacuum lines and stuff. There are several vacuum lines that aren't even hooked up and are plugged. Does anyone have a good vacuum diagram for this model and year?
 
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