Classic/Antique Car Repair: chevy single barrel 235 carb, piston cup, hesitation problem

Question
QUESTION: i rebuilt the carb off my 1956 chevy 210 everything is stock. it was my first rebuilt attempt and it wasn't very hard and the car does start now but i have to pump it to get it started and it hesitates when i give it gas only at rpms under 2000.when that happens it sounds like aloud hissing noise or allot of air being sucked in ? the only part of the rebuild i wasn't sure about was the pump piston cup it said it must be lubed and then flared  before installation. i did not no what was meant by flared. any insight for me? thanks in advance. mike in p.a.

ANSWER: We used to use a little brake fluid on the cup and then expand it so that it fits snugly into the bore. Make sure that when you put the cup in the open side is down. Good Luck.
Brad

---------- FOLLOW-UP ----------

QUESTION: would that be the cause of my hesitation problem? its almost like its choking its self out and this is while in the garage not on the road.

ANSWER: Is the problem at idle or when you try to accelerate?
Brad

---------- FOLLOW-UP ----------

QUESTION: when i try to accelerate.

Answer
The accelerator pump appears not to be working. With the engine off look down into the carburetor throat. Make sure that the choke is open. Use a light so that you car see and pump the gas pedal. There should be a squirt of fuel from the accelerator jet. If not the accelerator pump is not functioning. If you have fuel let me know.
Brad