I did this very thing to adjust my daughter's 1974 Dart Custom with a 318. The adjustment is easy to do since the top plate is easily removed and all it takes to adjust the spring lift is a small screw driver. I made small adjustments (1/4 turn) until the carb gave good response throughout acceleration. I knew I had it right when she came back a few hours later and said "Look what I can do Dad!" and she lit up a one-legger burnout.
