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1984 F-150 4X4 5.0 Carb Trouble.


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#1 Auburn David OFFLINE  

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Posted September 05, 2014 - 10:06 AM

I am in  the process of building the 3rd Carb for my old farm truck,the problem with it is it does great till you leave it idling and then it loads up to the point that gas comes out the overflow on the top of the 2bbl motorcraft carbs.

 I have been rebuilding these type carbs all my life and never had this issue before,always use new floats and needle and seats,I have adjusted the float levels time after time,even put a fuel regulator on it...there seems to be no fix for this problem...LOL



#2 Jack OFFLINE  

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Posted September 05, 2014 - 10:54 AM

Well one would think there are only two things that could cause this.  Needle and seat not shutting down or fuel pressure is to high.  Or both.  Sounds like you have that part covered.  So what else could it be?  The only other thing that comes to mind is heat.  As you say it only occurs at extended idle there are a couple things that you might want to think about.  I have seen fuel "blends" with a very low boiling point cause this type of issue and what about a heat isolating type of spacer below the carb. Does it have one?  I do not know if your truck has a heat riser on the exhaust manifold or not but I have seen them stick and force more exhaust through the passage in the intake manifold under the carb.  I cant say that any of this could be any help for you but its something to think about.  Good luck. 

Jack..   


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#3 Auburn David OFFLINE  

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Posted September 05, 2014 - 01:39 PM

you know that could be it,I removed the EGR plate on this engine when I changed the intake a few months back,it has a metal riser plate in place of the thick fiber gasket now..humm,I have to go try something different...thank you!



#4 TomLGT195 OFFLINE  

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Posted September 05, 2014 - 05:26 PM

I have to agree,that sounds like the culprit, I've had that problem with my older 302 in the past. spacer solved it. Tom



#5 Auburn David OFFLINE  

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Posted September 27, 2014 - 11:55 AM

I have to agree,that sounds like the culprit, I've had that problem with my older 302 in the past. spacer solved it. Tom

UPDATE!!!seems the bowl was warped just a little and when it would heat up it caused the needle to to stick somehow..not sure of the logistics of it..but the guy heated the bowl up and dropped it in oil and boom..no more problems..runs better than it ever has..seems even with the bowl warping it wouldn't effect the seat...but hey his fix worked!


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#6 Auburn David OFFLINE  

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Posted September 27, 2014 - 11:58 AM

Also,he said the reason is the cut on cast iron to aluminum intakes(all the carbs I tried were off cast)seems one twist one way when hot,and the other twist another..sounds crazy..but it worked.


Edited by Auburn, September 27, 2014 - 11:58 AM.

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