What can be done to stop the annoying intermitant run on after switching ignition off. I've changed plugs, plug wires, rotor, played with timing, swaped out carb (another used one). It's a little embarrasing to pull up in your bright shiny red lowered truck, all heads are turned then it sputters to a halt when you turn it off. :?

Check for vacuum leaks, idle speed too high and ignition timing advanced too far.

acauth1 has it about covered, only thing I might add is what grade of fuel are you running? Might need a higher number octane.

I'll check the vacuum, maybe rebuild carb. I run, well, whatever gas is cheapest when I need it, 87 octane. I figured that would be sufficient for a '80 229 ci V-6. I know the engine is kinda tierd, but runs okay otherwise. Just need to get by about a year longer before I go for the V-8 swap out, but this run on is really squashing my cool points at times. Thanks for the input.

Another posibility is the anti-dieseling solonoid. located on the drivers side of the carb. With the engine off, open the throttle and have an assistant turn the key off and on. You should see the solonoid extend and retract, to completely shut off the air. Hope this helps.