I had three different sets of Holley six pak carbs that I dyno tested on my pump gas 400 block pump gas 511 C.I. storker motor, the 1971 stock 440 carbs opened to soon so I had to change the outboard vacume pod springs to slow it down so it wouldn't bog They, six paks, rock on the street once you get them dialed in close I would remove the lead plugs on the outboard carbs to get to the idle mixture screws and turn them in gently to bottom them out and then unscrew them to 1/3 to 1/2 turn out from bottomed out and then use the center car. idle mixture screws for the final tuning Let us know how you like them