Ever since I put a new Holly 390 carb on my 272 it has had a flat spot when accelerated. (I never liked Holly carburetors to begin with but my son talked me into it). Cruising at a constant position on the pedal when I accelerate it will fall on it's face for a second then accelerate normally. I went through my Holly CD & tried everything it said. I changed the cam position & made it worse. According to the CD it should be the squirter but after setting the accelerator pump as per Holly instructions, I changed the accelerator pump nozzle (squirter) from a 25 to a 31. That made it a little better but did not eliminate it. I changed that one to a 37 & no change, maybe worse. I put a vacuum gauge on it & it is rock solid at about 14" at idle so I don't think there's a vacuum leak. I looked down the carb & actuated the throttle & gas squirts out of both squirters from any throttle position. I checked my timing & set it @ 10 degrees. I'm at my wits end. I'm about ready to get an Edelbrock carburetor & start all over.

Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL