I have been having this problem for a while if i nail it for a idel my car almost stallls.... but from a roll at like 2300rpms and up its fine i thought it was because it was runing realy rich so i jeted it down it runs a hair rich now but alot beter then befor any ideas ...by the way its a 850dp on a 496ci big block

 

Seems like either the accelerator pump cam, and/or the squirter nozzle size.

Too much fuel, or lack of fuel from the idle circuit to the main circuit will cause
a hesitation, or bog.

The accelerator pump cam can be changed to time the fuel shot. The nozzle
(squirter) is responsble for spraying the fuel into the venturi as the throttle
blades open.

It's trial and error. Trying to explain how to set the circuits would be near
impossible.

Buy a tuning kit for the carburetor with assorted pump cams and nozzles.

Start at one size and work your way up until the engine feels good off the
line. You'll know immediately if you're swapping in the wrong pump cam, or
nozzle.

The over-ride spring is also critical. WHen you change the pump cams, reset
the clearance on the spring to 0.010" with a feeler gauge.

 

thats exactly what its doing... i was watching it it throws alot of fuel in then bogs.... so all i need is the accelerator pump cam assortment kit from summit

 

Sounds like a lean condition. When you go to WOT from a dead stop, you're opening up the throttle blades really fast allowing a lot of air to quickly enter the engine when the engine is under it's most load. This is compensated by the accellerator pump squirting fuel in at the same time. Going to WOT when already moving, doesn't produce the same amount of load on the engine so it isn't as noticable.

A 30cc accellerator pump is usually fine so I wouldn't recomment going to a 50cc pump. Start by trying different pump cams and adjusting the pump as mentioned above every time you change the cam. What size are the squirters? They can be anywhere from .025 - .031. You could even try some .045's

 

i dont no what they are..... like i said the car was runing real realy rich ....black smoke rich....i was watching it and it looks like its dumping to much fuel froma stop

 

Check the float levels. Make sure fuel isn't dripping out the boosters when at idle.

 

the floats are fine

 

Check this link for tuning help, or at least the pictures to identify the items

http://www.domestic-street-scenes.co...ewtopic&t=2431

Nozzle/Squirter (large cannister looking thing with two arms pointing down)
http://chevyhiperformance.com/techar...mage_large.jpg
Accelerator Pump

http://www.popularhotrodding.com/eng...R_Carb05_s.jpg

 

after watching it witht he filter off when u crack the throtle at 1k large amounts of fuel come out of the Nozzle/Squirter it boggs down

 

OK, here's the deal with carb "bogs." Commit this to memory as there will be a test later:

ALMOST ALL BOGS ARE LEAN BOGS.

If you nail it and it stumbles it's lean. How do I know? Well, one of the ways is that you said it almost stalls. A rich bog will feel mushy like you just put your foot down in a bucket of cold oatmeal, but it won't try to stall. It'll just wallow around in the mud for a second and then slowly come back and pull normally. Also, you don't mention anything about a big puff of black smoke when you nail it. I can add 2 plus 2 and come up with 5 just as well as the next guy.

IF your carb is in good overall mechanical condition and there are no problems with the basic functioning of the primary or secondary accelerator pumps (that's a BIG "if" for a Holley, especially if it's got some miles on it) then your problem is most likely that the squirter sizes on either the primary or secondary are too small or the seocndary jets are real lean.

Is the carb brand new and KNOWN to have all the stock parts in it (at least as far as the accelerator pump systems are concerned)? If not, what are the specs on the carb now (yeas ALL of them- jets, power valves, accelerator pump cams, squirters, etc.)?
What is the List # of the carb? That'll be List 4781-X. What's the X?
Has the problem ALWAYS existed with that carb or did it start just after a "rebuild" or a jet change or an intake backfire or or or.....??

Carbs always leave clues like bad criminals. You need to be a detective.