I'd suspect the convertor is inefficient like others here do if he's
certain his tires are not spinning. He might have an off-the-shelf vert instead of one matched to his combo. That's a pretty big MPH/ET spread.
Here's some current NHRA records for automatics to show what can be done.
B/SA - 10.03 130.80
C/SA - 10.37 125.69
D/SA - 10.39 125.92
I'd get on the phone to Turbo Action and get a Model J. I had great luck with them when I ran the automatics with the big wedge motors.
