1959 cadillac hesitation

My cady hesitates from stop when accelerating just initialy and then runs fine while driving. I have changed plugs, electronic ing, wires cap, rebuilt carb fuel filter. What can be causing this???

Sounds like fine tuning the air/fuel mixture first, might be a little rich… then recheck the idle etc… A general rule is after gently reseating airfuel screws reverse out 4 turns and then back evenly 1/8- 1/4 turns till the hesitation goes away. The higher altitudes the leaner it will run.

Might have to recheck the float bowl adjustment if it’s ‘dumping’ (too full) or not enough fuel…

Do you have points? If so use a dwell meter. Also disconnect and plug vacuum advance line when setting the timing. Assuming carb rebuild included a new accelerator pump diaphram.

Is the accelerator pump in the carburetor working? When you move the throttle, it should shoot a healthy spray into the carb. If it isn’t, that’s likely the cause of your hesitation.

I’m with oblivion on this one. Your description sounds like an accelerator pump problem.

You may want to check the vacuum hoses for leaks.

Here’s what I’d do-
Check that accelerator pump is working
Check for vacuum leaks
Check timing
Check operation of centrif. advance
Check operation of vacuum advance
Check carb idle setting
Check choke operation

Also, in the right side headpipe, just below the exhaust manifold, will be a “heat riser valve” that controls the flow of exhaust gas through the engine…Make sure it is free and functioning normally…

Bogging off the line is usually caused by a lean condition, not a rich condition…The accelerator pump and power circuit in the carb are there to provide extra fuel during acceleration…

Hesitation ususally points to an accelerator pump problem in the carburetor, retarded ignition timing, or a stuck advance plate.

Who rebuilt the carburetor and how was it rebuilt? Some think a few gaskets and hosing it out with aerosol carburetor cleaner constitutes an overhaul.

You state this car has electronic ignition. Provide some details on that about type and timing, etc.

Accelerator pump, some of them had holes to adjust the amount of gas they spray for summer or winter or low or high altitude. When they go bad it is usually a split in the rubber diaphragm inside.

Seems like most likely a carb problem. Check the accelerator pump on the carb as has been mentioned. With the ethenol gas now available which the motor wasn’t designed to use you might want to go to mid grade or premium gas to see if there is a difference. There are also some additives you can buy to use ethenol gas in older motors. I find these additives help my '87 carbed 351 windsor V8 motor in my boat.