750 DP Mech 2nd's. On start and warm up car idles at 750 RPM. Primaries are alittle rich. When getting the car "hot" around 185-195 and driving, the idle increases. Can't find any vacuum leaks. Would the primaries running rich cause it to "idle up"? Would fuel lines possibly getting heated by headers cause this?

 

Did you spray carb cleaner around the whole carb when it is running?

 

Sounds like you need to adjust your idle mixture screws, try turning them out 1/8 of a turn and reset your idle if effected. Run it around and see if it helps. It is starting to run lean when the idle increases like your talking about so that means more air is getting in somewhere.

 

Carb cleaner, ether, brake cleaner, all but pouring fuel around the carb and vac lines, no leaks. Adjusted IMS using a vac gauge..9.5-10" at idle. Will try again. Noticed that if I pump the brakes idle increases. Ran car, shut off pull hose from booster and I get the rush of air. I read that pumping brakes effectively causes a "vacuum leak" increasing the idle. Possible problem with the booster? Check valve seems to be ok.

 

You will always get the rush of air. Pressing your brake pedal down will actually lower your rpm but when you release the brake the idle will pick back up. Does this happen when sitting or driving?