I have a 76' F-150 2wd with a 360/4spd in it. I rebuilt the motor, tranny, and the stock 2bbl carburator. I seem to be having some...issues...with the carburator because i can't get it to do anything but idle good. Heres my problem: I start the truck up and let it warm up, i open the choke, i drive it around for the first 10 minutes and it runs beautifully. After 10 minutes, the motor doesn't want to do anything but idle. I step on the gas and the motor begins to miss, rumble, and develop a low growl. I am completely stumped. I put the two mixture screws all the way in and tried to get a fresh adjustment at least 6 times now but i can't seem to get it. It almost acts like it is flooding itself out but my rebuild kit for the carb didn't give me the wet float level...it said "see service manual"!!! I bent it to the dry level and left it. Yesterday i decided to lower it about 1/8 of an inch, but the same prob still happened. I have no emissions on it, and the only two vacuum lines are from the distributor and the brakes. The timing is at 6btdc. The motor has duraspark II ignition. The carb is a stock 2bbl with manual choke. Keep in mind that it only does it when it warms up. Any suggestions???? Also, does anyone know the wet float level(from top of fuel to top of carb) setting?

 

Have you checked the advance in the distributor? It could be sticking when the engine warms up. Also, the outer ring of the balancer could have slipped, causing an incorrect timing reading.