I just bought this newly rebuilt 390 From this guy for my 68 f100 short box. Now having it in my truck it runs rough, it has a 1/4 cam from summit 262 intake 272 exaust. It only has a two barrel . Is this cam too big for this carb. Also stock distrubitor. Any help on a good intake and carb to match this cam.

 

well, i probably have more questions than answers about your 390.
when you say rebuilt, was it completly rebuilt or recently freshened up? do you have receipts or atleast a list of what the builder installed ( valve springs lifters etc ). did you break the engine in or was it ran prior?
i ask all this as you could have other issues other than a too small carb...........
however, in my personal opinion, if you want performance from your 390 definatly switch to a 4 bbl carb and manifold and make sure you have atleast a dual exaust, preferably headers as well.
does it run rough at idle only or is it running rough all over???
definatly get a pertronix ignitor or something similar to replace the points in your distributor.........as for manifolds, the edelbrock performer rpm seems to be the favorite other than high end ( dove ) or hi po factory castings.....although check e bay as they usually have manifolds and anythings better than the stock 2 bbl. as for carbs, 6 to 750 cfm holley or edelbrock shoiuld work although i tend to prefer 750's to everything as that way if you really start tweeking the engine you have plenty of carb.....

 

390 Guy! Welcome to FTE! I always start with an ignition diagnostic, followed by compression test, followed by an intake leak check. I agree with LFT on everything except on the intake and carburetor CFM. I believe the Edelbrock performer with a 600 cfm carburetor is plenty for a street driven truck. I would also add that there is at least a thousand things that could cause your truck to run rough. Gotta do the testing!