I'm thinking it's a transmission issue. Just replaced the 350 motor, new Holley carb, and replaced the slip yoke as the trans would leak if it sat for 2+ weeks. Have driven it less than 100 miles so far. First full temp drive, it wanted to stall at long lights, but only after having driven a while. Went back to shop and they adjusted the carb. Car drives and shifts fine, but after driving 20 minutes or so, the idle drops at lights and is a little uneven. Then, restarting while hot, the car wants to/stalls when put in gear. The car has always lurched a bit when put in gear but had never dropped rpms to the point of stalling. Otherwise drives and shifts great—no slipping, no bogging, strong accerleration. Searched and found some info on torque converter issues, but wanted to see what you folks think. Thanks in advance.

 

When the engine is hot and starts to stall out, what is the RPM if you shift it into neutral? Is it the same as before the stalling occurs, or is it lower than the no-load idle is normally. Obviously this will tell you if it is a trans problem or other. Frankly, it sounds like a vacuum leak that is opening up when the engine gets warm, or else some carb problem. What's the vacuum reading before and after the stalling starts?

 

Thanks Joe. I'll be bringing the car back next week to have them take a look for vacuum leaks when hot. (I do no real work myself). They set the idle high (about 1000) and I wanted to log some more miles before bringing it back in, but there seems to be no difference in the no-load idle, regardless of engine temp. Only when hot do the rpms flutter at lights or, after hot restart like today, plummet and stall. Successfully drove after a second restart today, but was alarmed by the amount of lurching.