This is interesting to me since I have yet to adjust the kickdown on my sbc 350 with Edelbrock 600 cfm carb and Performer manifold. Other folks will have better answers but you can help by telling the size of the engine, the intake manifold, the cfm of the carb, the degrees advance on your HEI and the plug gap you are using. I am amazed at the expertise of folks here on the Forum, but they need some specs to work with. To diagnose a problem from across the country without looking at the setup requires more information.

Don Shillady
Retired Scientist/teen rodder