i just bought a 79 f250 (400/c6/205... 44/60... 4" lift... 35's... etc etc etc) im new to the ford world, actully this is my first one.

the 400 is a recent rebuild, maybe 50k miles on it, its got some mild performance stuff on it (headers, performer intake, holley 600 and a rv cam) nothing to special, but it gets the job done untill a find a cheap 460.

ive been tweaking on this thing for a dew weeks now, trying to get rid of a sputter under acceleration... i tried rebuilding/replacing the carb, adjusting timing, new fuel pump... and nothing seems to be working...

if i roll on the throttle from any rpm it sputters slightly then i can feel it clearing out and it runs good and strong. if i just floor it from any rpm it falls on its face, coughs, chokes, sputters, then takes off...

anybody have any other ideas on what it could be? :confused:

sounds like a carb or timing problem to me.
couple things i'd check:
1.) are you sure it's a holley 600? does it have accelerator pumps on both ends?
there might be too much fuel when you hit the throttle.
2.) does it do it out of gear too?
3.) make sure the timing is on for sure. is the harmonic balancer stock? or from a different rig? it could have the wrong marks on it if it's not. check that out. set it on tdc by the marks, and shove a screwdriver in the #1 cylinder, if you hit piston, you're good there. if you don't hit piston, try one revolution from there, back to tdc.

accelerator pump circuit
*EDIT and it wont fall on its fac from too much fuel, it is lacking a pump shot

accelerator pump circuit
*EDIT and it wont fall on its fac from too much fuel, it is lacking a pump shot

X2 what he said.

thats what i was thinking to, but it does it no matter what carb i put on it... i tried a marine 600, a edelbrick 600 and a 600 double pumper... none of the carbs were "new" but im sure they cant all be bad... i just did a full master rebuild on the marine carb, ill put it on tommarow on my lunch break and we shall see what happens...

yeah the 400's like a big carb (i had a holley 750dp on my stock 400, and it used every bit of it), so check that, verify the timing as said above.

accelerator pump circuit
*EDIT and it wont fall on its fac from too much fuel, it is lacking a pump shot

Often times, the problem with the holleys in a heavy truck isn't the volume of accelerator discharge, its the duration. Most times you need to go to a smaller center squirter rather than a larger; as this will lengthen the discharge time and overcome the weight of the vehicle. I can't tell you how many guys have scratched their heads over this until I turned them onto this little tidbit.

The problem here, is that you are currently running a 600cfm. It will probably already have a #25 which should be adequate. Still, verify the squirter size (it will be stamped into it) and then size down if it has one of the bigger units (which guys will commonly swap too not understanding the actual physics of how the center squirter works).