I have a fully rebuilt Carter 3211S on my 57 235 engine. The idle adjustment screw does absolutely nothing in regards to the vacuum reading (at manifold). Engine is running at 500 RPM idle, timing at 5 degrees advanced. Each time I turn the screw a quarter turn, I bump the throttle but still nothing. I would have thought that the idle mixture screw would at least have an effect on engine RPM but it does nothing throughout its travel (until it comes all the way out at which time the engine dies, or turned all the way in and it runs terrible). I left the screw at 3 turns out from bottom. Anybody have any ideas on what would cause the idle mixture screw to have no effect?
