Two brand new converters, one 5000 and the other 5800, has tried leaving at numerous different RPM's........ While it certainly could be a converter issue, it would seem as though this has been ruled out. I still say a footbrake launch might prove interesting...... Besides being easy and basically free.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads