I've heard on this forum from just about everybody with Vortec heads, that the max lift is .480 until the retainer is smacking into the valve guides... Well, according to this website the max lift is only .450 and I'm not sure who's right. My heads are from a 96 (I think) Vortec truck. They're the 906 L31 heads. I've installed new springs on them. I'm running an LT4 standard cam (.447" lift) with this combo. I figured I'd be safe.

As some of you know, my car is not starting at the moment. Someone from a different forum told me that I probably bent my pushrods, because Vortec heads are NOT suited to .480 lift as I thought they were. He sent me that link above, and told me that he uses the same Vortecs in his setup. I'm going to check my pushrods when I get back to my car first thing... because I'm scared I may have over-lifted the heads.

 

http://www.chevyhiperformance.com/howto/97458/