Well, they ran fine on my stock 350 in my truck. The truck is getting a pair of Vortec heads. I haven't run the truck with standard valve heads so I can't tell you if there was a difference. I was planning on having them rebuilt with standard sized valves and putting them on my boat along with thin head gaskets to tighten up the quench and bump the compression some. I believe they have bigger runners than the 461 heads.

Oh, the head don't have oversized runners if they don't have the X at the end of the casting number.