I've always heard that Vortecs will only take .400 lift, or .420, wait, maybe .460, no no, .480. It seems every Smokey Yunik wanna be with his own website and these heads has their own figure. So I went to the source and asked the one who would know, the general himself (GM). Actually Pace Parts, but anyways, out of the box GM reccomends .475" and Pace says that you can get away with .480" I guess they should know because they also doing in house machining on these heads accept lifts in .500"+ range, I think they call them ZZ5 or something. I feel better about my .460 lift on my Vortecs.