I own a 1987 F250 with 351w 4bbl. carb. The problem is with the carb. on this truck.In the cold damp days it runs terrible and uses a ton of gas, and it will not idle once it comes off the choke. If I shut it off and let it sit for awhile it seems fine. This carb looks like a holley but a holley kit will not work on it gaskets are different.Can anybody help with suggestions.I rebuilt this carb,about 1 yr ago and it didnt help it,I have owned several vehicles with holleys and never had this problem before.

 

Do you have the stock air cleaner, with a functional heater? There should be a 2"-2.5" metal hose going from the air cleaner horn to the shroud on the exhaust manifold. If this is not there, or the valve is open to outside air, then the carb can get iced up, especially in the conditions you describe.

 

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Thread moved to Carburetion forum.

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Yep, sounds like carb icing to me too. Pretty common in the winter when the hot air assembly is not there or not working.

 

I had a 87 F150 with the same motor and carb and the same problem,just learned to deal with it as a friend has a holley on his 65 mustang and 67 F100 and I have one on my 65 galaxie and they do the same. My 87 had the hot air system working and it still did it so the carb spacer might not be letting the carb warm up quickly enough,I think those took the thick carb gasket between the carb and spacer and putting a thinner gasket under the carb might help but might get the carb too hot in warmer weather. I noticed my 65 custom 500 doing the same with a motorcraft 2 bbl so it could be gas quality too making carbed vehicles to act like that, Jeff

 

Mine does it without the hot air hooked up, with it hooked up, it doesn't do it at all.

 

I fully agree, it sound like classic carb icings in cold damp weather from lack of preheat. What happens is as the gas is vaporized into the airstream is lower air temp below freezing the the moisture frezes on the throttle plates disrupting airflow. Preheat air prevent this. It will be its worse in the 40's and 30's when it is damp too.

 

Thanks for all your help, I have had several holleys on other vehicles ,and how I use to do them was start it up and let it run for a few then shut it off and let it sit. I put carter afb on one and the problem went away. Not sure why holley does and afb doesn't seems kinda weird.

 

I am experiancing the same thing with the same model and year truck. It takes 10 minutes on cold days to warm up and stalls constantly until it is warm. I will check the air system.

 

HokieJones
I replaced the holley.ford carb on my 1987 and the problem is almost gone and i get better gas mileage. Also on the drivers side on the intake just below the throttle linkage on carb there is a vac. canister attached to a small linkage, this controls the heat going acroos the intake(exhaust) I opened mine up all the way it was closed this helped out also.As for my 2 cents I say get rid of Holley half breed and buy carter afb or edelbrock and swap it out.

 

Thanks - I will look into this. I am not familiar with Edelbrock. I have never replaced a carb before - is it a difficult task?