I have a 1967 f100 (352, 3 speed on the column) thats having some problems. We recently did a motor swap, swapped the old 352 that had a dead cylinder and some other problems, to another 352 that we had sitting in our parts truck. We swapped motors, exchanging a few parts from the old one, including the carb. After getting everything in and doing the basics on the motor it ran pretty good. There were no problems from what we could tell, except for the carb gasket leaking, we replaced it and it ran great. After letting my dad drive it to work (about a 7 minute drive at the most)for a pretty good while (probably about a month or so) I decided to drive it to school(about a 30 minute drive). It ran fine until I got to the head of the creek when i had to come to a stop and while down shifting it cut off. It had done something similar to this when we were testing it but it was low on gas and we assumed it was almost out and thats why it tried to cut off, but it hadnt happened since. I started it back up and got on the highway, everything ran great until I got to my school where it tried dying out again and when I parked it, it was idling really rough, the idle would flucuate. After school, I started it back up and it was running fine, but after it warmed up I drove it to the school exit where it cut out again. On my way home, it would run fine until i would have to come to a stop, where it would try to cut out while i was downshifting. In total it probably cut out 6 times before i got home. At home it was idling poor and we tried adjusting the air fuel mixture screws on the carb (think its a stock carb, guessing a 2100 series 2 barrel) and it helped some but not enough. It still idles very rough after getting warmed up and drivin for a bit. The idle will flucuate, but the motor doesnt completely cut out. The thing about it is though is that it runs fine with the choke pulled out. So its like its getting too much air or not enough fuel after it gets warmed up. Im guessing and hoping that its probably something to do with the carb but want some opinions from others. As far as i know there are no other leaks on it. We have checked. Want to get this truck fixed asap. I love driving the old girl. Any help would be appreciated! Thanks!

 

Could be trash in the fuel system or, if you have a points ignition, it could be a condenser that's on its way out.

 

Make sure fuel delivery is @ spec. 1 pint in 30 seconds at idle. It won't burn this much - honest injun - but Fuel pump has to be able to provide that much at all times, under all conditions. Probably best to replace any fuel pump more than a few years old, blow out the hard lines with shop air and replace rubber hose.

Then - this is important- make sure float height is correct. Even a 1/16" can make a big difference. If the fuel pump is weak and/or the float height is incorrect, clogged lines, leaky cracked hoses etc, it will never run right.

 

Thanks, I have another distributor that i could try or get some parts off, and Ill check the filter on it and see if its got anything in it, might replace it and see. Then ill go from there. Again thanks!

 

Thanks Tedster9, Ill check into it

 

*update* Got alot accomplished today. Checked alot of stuff. Float got stuck and had to fix it, wound up putting another float in it from the other carb while we were trying to fix it, got it fixed, wasnt stuck anymore. Found a vacuum leak on the carb. Fixed it. Idle improved a little. Found 2 of my spark plugs were loose for some reason. I have no idea why they were loose. I dont think we would have forgot to tighten them so i really dont know. My inline fuel filter was leaking and found out the threads on the carb was stripped. Put the other fitting on with some thread tape and got it tightened up so hopefully that works. We took the other fuel filter on the motor off and inspected it. For the most part it looked pretty clean but the filter was in a little rough shape so gonna try to replace it soon. The fuel in the filter was clean but there was a bit of debree in the bottom. Changed the distributor cap and rotor button. Changed the condenser. Filed the points a bit. After the work on the distributor, the motor really picked up. The idle wasnt nearly as bad. Still seems like it may be a little off. Gonna check a few more things when i get the chance. Applying the choke doesnt change it now, there isnt a difference. Ran it up and down the road a good 5 or 6 times and it ran fine. Gonna let dad drive it to work and see what happens. If everything works good might attempt driving it to town on a weekend and see how it runs. Is there anything else you all would recommend me check, because like i said, its better but i wouldnt say its perfect. Still need to actually check the vacuum, need to get a gauge. Would like to check the fuel pressure. So im really glad its running a little better, maybe its fixed, i dont know. Only time will tell i guess. If something ill comes up or if it starts acting up again ill let you know. Probably gonna let a friend of our check it out to, see if he can figure out anything wrong with it. But again if theres anything else you think i should check please let me know. Thank you!

 

Sounds like you're on the right path.

 

Yep that's progress. Make sure the vacuum advance diaphragm isn't shot and is holding. To check for vacuum leaks, an unlit propane torch cracked open light works good. If the idle picks up you've found the culprit. While that isn't really a fire hazard, messing around with carbs and floats and filters sure can be. Keep a full size CO2 (no mess) or ABC fire extinguisher on hand in the truck and garage.

Yep get a gauge on the manifold to see how much vacuum is being drawn at book idle RPM. They will point the way for tuning too. There's really no substitute for that.

 

Once you filed the points did you adjust the gap to be correct? Also check the timing.