Might try swapping them again just to check. Sure seems like an idle circuit. I didn't see but have you taken every vac source out of the equation? Spraying carb cleaner around the intake? Timing close?
I may try swapping them again. Before I swap the carbs again, I'm going to take every vacuum source out of the system. About the only place where I got a rise in rpm with the carb cleaner was at the #5/#6 cylinder. The timing is as close as I can get it with the high rpms.
Well I headed over last night to work on this 77. I never got around to finding the high idle problem. Went to turn the key to ON and engine just turned over with no start up. I have fuel in the carb sight glass. Hooked up a timing light to see if I was getting any spark. Timing light would only light up when I moved the key from ON back toward OFF. I'm going to order an ignition switch on Monday. I believe the ignition switch is bad anyway because even before the no start issue came up, I had the problem of the engine would keep cranking with the key on the OFF position. I think this will solve the spark issue also.
I don't have any results with the only running at idle with full choke. Seem to have a new problem. I put in a new ignition switch thinking this would fix my no spark problem, but it didn't fix it. At one point I had spark, then the next time I had nothing. Checked tightness on a few parts and spark never came back. Started looking at other parts for this no spark problem. I took lead off distributor that comes from ignition coil and checked for spark. Held it next to a bolt and cranked engine, no spark. Checked the positive side of coil to ground with the key ON and the points open and there was nothing. Book said if you have nothing, check the wiring from the switch. I wanted to take a picture of the coil and igniter wiring to make sure it was wired correctly, but forgot to take phone last night. Any thoughts?
I put the new switch in. Cranked it and had no spark. Tried a couple more times and no spark. Tried one more time before I started digging in and had spark. Went to try and start it and had no spark again. I have a Haynes and a toyota repair manual.