I have a 78 f-150, 4x4 with a manual tranny. I have tuned it up and cannot get it to run right at idle. Fast idle is fine. I was going to rebuild the carb, but it is a rebuilt carb(bought, not owner rebuilt) and does not have the factory numbers to get a rebuild kit for it. Their are apparently about 15 different variations of the one bbl carb used on these trucks. If I buy a rebuilt carb should it work properly since I don't know what model was on here originally. If not is their anything I should look for on the rebuilt to try and tell what carb they replaced it with. Physical characteristics as the rebuild numbers on the carb are from the company that rebuilt it and don't cross reference to anything.

T. Roberts
UFD Local 1147

 

There might be 15 different carbs available but there are probably only three or four kits for rebuilding all of them. My guess is that if you take your carb apart and bring the pieces to the parts shop you should be able to match up to the gaskets and parts in the kits. Probably what your carb really needs is a good cleaning. If you only matched up the gaskets you could put it back together. the Main jets, floats etc. don't even need to be replaced unless you actually find something wrong.

 

well, sounds like the same thing I had.....the carb was fine bought 2 of them & same thing. I took a spray bottle of alcohol & shoot around the manifold & carb base & the engine revs up. & my EGR was sucking air too. so you might try this easy inspection & see what you find or not then you know its the carb.

 

The truck more than likely has a Carter YFA. Basically an emissions version of the trusty YF. I recently bought one of those rebuilt jobs. I ordered a 1968 model Carter YF to run in my 65-300 and replace the testy Autolite 1100. At about half throttle I hear a whistling sound which is all too familiar. Throttle shaft end play. I have looked at other rebuilts at a parts store and several had end play. I knew this one had a little bit but was anxious to get on with the conversion. I pretty much expected to go through a few warranty swaps in order to find a good one. The carb seems to cause the engine to run better in ways but it seems to periodically go a little goofy. I need to correct a possible ignition issues before I write this off as a carb problem. Thing is I had the ignition issue before I changed carbs and did not have this problem. With a timing light my mark periodically jumps what looks to be 6 to 8 degrees.