Carburetored type IV engine problem diagnosis., Engine idling problem. Options

[Keith914]

Just completed very careful cleaning, installing, adjusting, balancing two Weber carbs on my recently rebuilt '72 1.7 type IV 914 engine upgraded to 2.4 L. Carbs are real Webers (Spain), and we're working well earlier. Balancing and setting idle at 1,100 rpm was done on cold engine - nice smooth idle and solid response to accelerator action. The carbs are 44's, idle jets are 55's, main jets are145's and the air jets are 200's. Sea level ambient condition.
Engine starts immediately and runs very well and continues to run very well above about 2,000 rpm. But once engine is approaching and then at normal operating temp - 190 F, it will not run smoothly below about 2,000 rpm, and at idle accelerator position, engine drops below 1,000 rpm and stumbles to stalling sometimes with pre ignition sounds as it stalls! Timing is set at 32 degrees at 3,000 rpm, and distributor is new with new Pertronix electronic unit, and no vacuum mechanism.

Welcome any diagnosis suggestions.

[Elliot Cannon]

My type IV is 2.2. I also have 44idf Webers. I've had them on the car for about 13 years and just recently rebuilt them. After rebuild it still ran like crap. I again checked the idle jets and found the jets on the passenger side carb were hopelessly clogged. Even after a thorough cleaning and rebuild. Cleaned them out, car runs great. I use 130 mains, 175 air jet, 55idle jets and 34 venturis. What size venturis are you running? Maybe try a different size vent. My experience with Webers is, you need to start with a jet combination then trial and error from there. I tried different combo's till I found what works for me. Try using smaller mains and air jets. You may also find your venturis are too large. (or too small) The syncrometer is a must have for balancing the carbs. I followed this advice for float adjustment. https://www.youtube.com/watch?v=54uPwTZ3DJw