mongolchuck

I have an 85 GT with a holley 4160 600 cfm. I bought the new carb in june and have tried tuning it ever since. I get a big stumble everytime i hit the gas hard. I've adjusted the accelerator pump arm, and changed the shooters from bigger to smaller and back again. My timing is advanced about 12 degrees. I still can't get the hesitation out. What is the best way to adjust this? I've heard many conflicting opinions. I'm also at about 5000 feet if that makes a difference. Any help would be greatly appreciated.

fourfivefour

Does your distributor have vacuum advance and is it working?
Did you try a little more base timing?
Did you adjust your idle mixture screws?

PRO50SC

Are you sure you're getting a good hit of gas from the accel pump. Also, have you checked to see if your vacuum advance is working? Your timing is advanced to 12* or by 12*?

fourfivefour

^^Beat you by 10 seconds. LOL

PRO50SC

LOL I saw that.

67mustang302

What's your initial/total timing? And how fast does it come in? Carburetors are rather sensitive to improper ignition timing. What exactly is the stumble you're having? Define stumble.

mongolchuck

I'm not sure the exact timing because i don't have a light handy but it is advanced a little past the mark on the intake. The stumble is the engine bogging down and cutting out all together if i really step on it. It is really bad from idle but there still is a little hesitation if i hit it when my rpm is over 1500. I just replaced the distributor and did check the advance, it works fine. I am getting a pump shot.

splash21

i had the same problem with my holly 600. i readjusted my timing and fuel pressure and it seemed to take it away. i would step on it from a slight roll and it would fall flat in the bottom but once i got the rpms up a bit she was gone. i even ran a 14.2 at the track because of this but it wouldnt do it all the time