Ok, a little back story. We bought a 1973 F250 Camper Special a couple of months ago. It's beat up, but when we picked it up it ran great. Idled fine, ran fine, made it home (30 miles or so) no problem. Spend the next couple weeks driving it around our little town, everything is still fine. My wife was showing her dad around one of the fish farms here on a hot day, and it starts running pretty rough. Gets it home and parks it and waits for me to take a look at it.

It would start but only if you gave it a lot of gas, and it missed like crazy and ran like crap, blowing black smoke until you got it revved up over 5k or so at which point it cleared up and would idle and run fine. It would do this off and on for another week. Replaced the fuel filter on the carb, and added an inline one. Cleaned and reset the points, checked the vacuum lines and replaced one that was obviously bad. Seemed to clear it up and was running fine.

Wife drove the truck to Les Schwab to get the tires balanced (30 miles one way) and it did fine the whole way there. Kid in the bay had trouble starting it once they were done, but got it going and it ran fine back home, until she turned it off again. Back to the same symptoms as before, but worse.

Scoured the internets for possible problems. Oil smelled like gas, so replaced the fuel pump and changed the oil. New points and condenser, new plugs, ran some seafoam in the tank. Distributor cap and rotor seem to be fine, as do the plug wires. Checked inline fuel filter to make sure it wasn't clogged with things from the tank, but its clean.

More tinkering with it today, and it is better but not best. Will start, sometimes with the missing and black smoke. Once it is going it will run through the entire RPM range in park just fine. Once you put it into gear, it starts running rough, and wants to die. When you get driving, it runs ok until you get a little speed, then acts like it is going to cut out. If you punch it it will pick back up, sometimes it starts running fine after that, sometimes not.

Tomorrow I am going to borrow a timing light from the work maintenance guy and check the timing, and am looking into how much a rebuild kit for the carb (Holley 2bbl List # 7508-1) will be. I am looking for any ideas as to what else I should be looking at as well. Possibly intake manifold gasket? Any help is appreciated!

James

 

To me it almost sounds like you got a piece of junk in the seat for the needle. Do you have fuel coming out the vent of your carb?

I believe this to be because when you rev it to 5k its using enough fuel to have the seat unplugged, and its just keeping up with demand