I was kinda shocked to see how much grinding you have to do to get 21cc out of a head. I’m not big on pouring a runner because honestly I don’t reslly care but curiously got the best of me so I poured a runner on my best set of Edelbrock heads that hit 318cfm with a 2.08 valve and I was right at 191cc. The old Doctor J heads claimed to be 220cc with the OLD company that made Speedmaster heads after he had them made without water in the floor. I honestly don’t think you could get 220 or anywhere near there without pushing the pushrod WAY over to gain area.