I'm not sure its realistic to think that folks out there are cc'ing worn out high mileage heads just for the heck of it. But just in case, here's how much it would matter...

Hypothetically speaking, lets say I cc a worn out set of heads with valves sunk 30 thou into the seats...

[(2.08"/2)*3.14*.030"+(1.74"/2)*3.14*.030"]*16.39cc/1ci=2.949cc...

Not even 3 whole cc's.