Tony P,
Tuning the modular 4150/4160 holley carb is something of a lost art. The page included below is the best explination of a step-by-step method for carb tuning.
http://www.bob2000.com/carb.htm FWIW, I used this with a 600cfm Holley on my 283. It's way too much carb for the engine, but with proper tuning, vacuum secondaries, and a 3.08 rear gear, I get 20mpg in my '56 hardtop. (at 65mph)
Gene
