So in 20+ years I'm actually following the manual to tune my 400 bird. The mixture screws are common sense and I've always used a vacuum gauge with a RPM gauge to set them just right. Now, the idle speeds are somewhat strange....My car has A/C so I do have the solenoid. I warmed up the car and adjusted the hex on the solenoid to get 650 RPM (with the tranny in Drive). wow it must be in Drive! Then I disconnected the solenoid and adjusted the carb idle speed screw to get to 500 RPM..still in "Drive". Then I set the fast idle to 2500RPM!!! as stated. Wow! These speeds seem really high especially the fast idle. I don't think I ever heard a car doing 2500 RPM at start up, and the regular idle being at 650RPM in Drive is idling at almost 800RPM in neutral now. What do you guys think? Is that were you have your speeds set at? BTW: Timing set with vacuum hose and solenoid disconnected.
Last time I set a high idle, I remember instructions with similar very high RPM ratings. But that is for the very highest setting of the fast idle cam. IIRC, I had to always manually force the cam to the highest setting.
What you will find is that when you set the choke and the high idle for a cold start by flooring the gas pedal - the bimetal spring is warm enough that the carb never sets to that highest cam setting for high idle.
One of our master engine specialists will likely come along here with better details.
1967 FB 400, original CA car (smog), now 455, finally in Paint Jail after 19 yrs. Metal work & block sanding done. Jambs painted. Color coat on, color sanding underway 2006 Mustang V6 Pony, factory ordered, 29 K miles, retirement cruiser and future classic(?) Old projects, gone but not forgotten: 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI