OP, when some changes don't make sense on the results there is usually a reason for the no change results I like to make sure of the basics first like the fuel supply, shift points,RPM drop on teh shift(converter effeincy) header length and so on. Can you fatten the carb. up enough to slow the car down in the 1/4 mile? If not look at the fuel supply, if so look try shifting it sooner or later and look at the RPM drop on the shift into high gear. If the converter won't let the RPM drop below 4500 RPM no matter when you shift it look at trying another one of your other converters that you know will let the RPM drop enough to get it close to 4000 RPM on the gear change Let us know what you do and find out BTW, what RPM are you shifting at now? What is the RPM drop on the shift?