I have a 1977 f250 with a 1976 460cid that is spitting and sputtering at about 2000rpm. Rebuilt the carb, New vacuum advance, New plugs, wires, cap and rotor. Checked timing. Fixed exhaust leaks. Wasn't spitting before I replaced everything and seems to be getting worse with everything being done. Any ideas as to what could be causing this?

 

Just going to ask a few questions to make sure they were checked ..
1) Choke is opening when motor reaches operating temp
2) Fuel filters changed
3) Fuel pressure is good/fuel pump is good
4) power valve was replaced when carb was rebuilt
5) float level was set at rebuild
6) what carb are we talking about ?
7) all vaccun lines are connected

 

I would say to double and triple check the firing order and make sure the wires are all in the correct order.

 

At this point, We have replaced the manifold gasket, plugs, wires, cap n rotor, vacuum advance, vacuum lines, rebuilt carb, new exhaust and set timing. The shop working on it is now saying that it sounds like valve timing???

 

Was any work done on the internals of the motor?

 

Not as of yet...

 

If it wasn't doing it before something was done but it is afterwards, it's usually a pretty safe bet that whats causing it is something that was done to it. Just because somethings new does not mean it is good, almost sounds like a crossfire deal. Cracked cap or wires shorting to each other. Run it after dark and watch as you rev it up to see if any sparks jump from the wires. A cracked cap can be almost impossible to see sometimes too..