we run Cast Dart Iron Eagle Heads 215 runners on a 406 and make close to 500 hp on a small 5.20 flat tappet camshaft. 10 to 1 compression ( pump gas motor)..holley 750 carb still got the choke horn,,,we also drilled for steam holes cause we street drive it..we could easily go over 600 hp or at least 600 with a more agressive roller cam profile..
i also had another 406 i ran some cast World heads ( dart)..mild port work 11 to 1 compression . 670 solid roller ..did some block work and ran aluminum rods and it made 620 hp...1000 cfm silver claw carb
Brian
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Bjuice..
"I'M YOUR HUCKLEBERRY ! "