I can honestly say I would never do this for a paying customer. Brett has a set of Edelbrock heads he did for Im guessing a super stock racer where the head had to come in at 170 cc runner and 2.02 valve. His buddy welded and raised the port so they could raise the runner. If I remember right it flowed around 280 cfm and cost between 10,000.00-11,000.00 to have done.