I have a 1970 429 backed with a c6 transmission. When I put it into gear, drive or reverse, the engine stalls dramatically. I raised the idle and it keeps it alive and is drivable however it’s really hard to stop. It feels like the engine is connected directly to the transmission and the torque converter isn’t doing its job. At least not very well. I’ve replaced the distributor, timed it, adjusted the carb and checked the vacuum lines. It purrs in park/neutral like a champ. Starts on the first try. Revs great in park/neutral. Please help!

 

Would be helpful to know more specifics. I feel it is an under performing engine. Torque converter is possible but rare. How's the plugs, fuel filter, carb/choke linkages? Has the points and condenser been replaced recently? Have you checked the point gap/dwell? What is the idle speed and base timing set to? May be helpful to connect a vacuum gauge to the maniford to verify a steady 18-22 inches of vacuum. If all that checks good, I would start with the carb.