Because the way that tight converter loads the engine. You want the converter to flash above your lowest cruise RPM. I’m betting whoever it was sold you a converter with an 11 inch case. I would think a 10 inch case would be the biggest and probably a 9.5 inch case would have been better. It may have only went 3000-3200 but that’s a grand above what you have.
Those tight converters load the engine harder at lower RPM, changes the timing curve you can run and affects how the engine makes RPM.
