they are a good head that works well mine flowed 317 with a 2.055 valve and they went every bit of 650hp on a 416

70 duster full chassis super pro 416 CNC Indybrock heads 727 w/brake

best so far 1.212 60 6.219 in 1/8 at 110.88 9.768 at 137.81 1/4