Originally Posted by DoubleVision
First thing I suspect is the mechanical timing advance is sticking open. Don't matter what springs or weights are in it either. After a while if they get gummed up, and they all do, they will stick open and cause all kinds of headaches. What carb are you using? Because of how it's acting I don't think you have a vacuum leak, but it is something to check. If the carb is a 4 barrel the secondaries could be slightly sticking open which also happens at times as well. I used to have a Demon carb that had a bad habit of the secondaries sticking slightly open and I had to sand the burrs out of the base plate to stop it. See if you can get it to idle high again then check the secondary linkage to see if it's open any.
Thanks for these thoughts. As far as the mech advance sticking, how can I check this? If I turn the rotor all the way to the stop bushing, it will snap back easily. Is there another test for it?
As far as carb, I can't recall, but I will check on it tomorrow after work.
Thanks again. I'll keep this updated until I can figure it out.