What is the lowest practical idle speed with an Atomic TBI system? I have put a TBI system on an old Cadillac engine before and the problem I ran into was trying to get a relatively low, stable idle speed. The old GM Hydramatic transmission stops slipping at a relatively low speed, much lower than modern fuel injected engines typically idle. The factory idle speed for a 50s Cad engine is 375-400rpm or so to accommodate this fact. If you are idling much above 500rpm, the transmission wants to creep forward and changing gears from D to R and back is difficult because the engine is transmitting too much power through the transmission (not slipping enough). So my question is: if one is to use a stock Hydramatic transmission on a mid-50s Cadillac engine (say a 331 or 365ci Cad engine), how low can the idle speed be set using the Atomic TBI system? In my prior experience with a TBI system on a 1949 Cadillac engine, the engine started instantly, gave good fuel economy, had great throttle response, etc. It also was completely impervious to vapor lock, which is the NUMBER ONE problem with cars of this vintage (IMHO). Fuel injection, like the Atomic TBI system, could be a good approach to solving vapor lock and hot soak issues for good. But if you can't make it idle low enough to work with the stock transmission, few will adopt it. Pictures of my former 1949 Cadillac with fuel injection attached. Attached files.