I'm having an issue with my Carter YF 2100S running rich. I am also having a problem with keeping the idle at the set RPM. I will set the carburetor idle at around 550 to 600 RPM, adjust the air/fuel at around 2.25 turns outward and get a good vacuum reading at close to 18 or 20 inches. I'll drive the truck for around 100 miles or so and the idle will drop to 350 or so. I'm puzzled.

Jon G had a great post awhile back regarding the diaphragm housing being warped and leaking gas. I need to pull the carb to check that. The timing seems fine. My question is could the drop in idle and the carb running rich be related? Could it be a small vacuum leak at the throttle body or bowl?

Thanks.
MarkT

1956 Chevy 3200, 1/2 Ton, 235 CI
https://photos.app.goo.gl/TQQo1YnFjs3U7xB57