canfield heads?

I know of a few guys that have used them. One had a 11.5:1 comprssion 331 with 175 shot and ran a 11.05 in a full weight 93 Limited yellow vert. Another has a set on a 306 and has run a 12.70 @ 110 (traction probs). And I guy I just met runs them on a 347 with 2 stage N20 and busted out an amazing 9.70 @ 140 in the 1/4...