Troubleshooting help desperately needed...

[budbeater]

This is going to take some background so it will end up long. Please bear with me because I need the help.

My truck (1971 Chev, 355ci, Edelbrock 650 Carb, HEI ignition) was idling high so about a month ago I messed with the choke (electric) because it seemed like it wasn't set right to disengage. I cranked the setting down and it seemed fixed until the next morning. The next morning I went out hunting (about 1 1/2 hour drive) I stopped in a small town to top off on gas. About 3/4 mile outside of town the problem started. The truck would be driving fine and then with no warning would violently shudder as the engine would cut out and restart several times in less that a couple of seconds. Then the engine would shut off completely. Sometimes it would just shut down with no warning. Sometimes it would just buck and jump as the engine would cut out and restart rapidly. The lights and the rest of the electrical system would never even flicker and the truck would start back up easily even while we were still at speed. Getting home on the freeway was horrible. In what seemed to be completely at random the truck would rapidly stumble and shut off like described before.

At first I thought I had over adjusted the choke, so I adjusted it back incrementally several times. This has not helped. In fact yesterday I disconnect the electrical input to the choke and the problem stayed exactly the same. Then I thought that I got bad gas at the station in Snowville, so I added some water remover and I have checked my filter, but nothing seems clogged and I have put in 4-5 tanks of gas since. The stalling seems to be too rapid to be fuel loss.

I have noticed that the problem is somewhat temperature related. It doesn't seem to start until the coolant temp guage goes over 180. It also seems to be worse when the air temp is warmer.

Also the problem seems to be slightly worse under some type of load (going up a hill, starting from a stop, accelerating)

I am wondering if the problem is a short in the HEI ignition. I don't know what else it could be, but I don't want to spend money on a new coil, module etc if that isn't the problem.

I have only had this truck about 18months and I am slowly going through it to upgrage and replace anything worn or broken, so I know that I have inherited someone else's issues.

Any Ideas? Any trouble shooting that I have missed?

Bud