Hey Scotty,
I finally solved the constant fast idling on my 1979 Pontiac Catalina's Rochester Dualjet! It turned out, the automatic choke was actually set too tight and keeping the plate from opening up all the way. It would stall out after I made the adjustment like it was air starved, so I slightly turned the Idle Speed screw inwards, following your older video tuning the carburetor on the 70s Corvette Stingray. It was almost completely retracted. No more ridiculously fast idle or stalling! Thanks for your help!
Here's a link to a recording of my final speed.
P.S. doing one of your new documentaries on how carburetors work and the industry change to electronic fuel injection would be quite interesting!
Congratulations! Usually when you have those kind of problems it's because the linkage is binding up somewhere, but figuring out where "somewhere" is can be a challenge.
I stopped messing with it for a few days this week because of the heat. I started tinkering with it again Thursday and pushed the choke linkages down manually a bunch of times. It didn't feel like anything was binding. It stayed there until I touched the throttle, then sprang right back up. When I noticed that, I knew I was zeroing in on the culprit. I actually hoped you might have had an opinion on it. Scotty said to definitely try the solution I came up with. I drove it around my neighborhood until it got hot and it stalled. No vacuum leaks, so I checked that screw. That's all it was.
Scotty has a heck of a lot more experience than I have, he worked professionally on those for a lot of years and has pretty much seen it all.