somewhere between 2 and 3 hours into this one head as of right now. These are factory heads off a 1989 or 90, 9C1 Police Caprice. I'm just doing my own portwork to open them up a little bit. Want my 383 to breath. All I've done is radiused the edges around the valve, radiused the valve guides, removed ugly castings that stuck into runner, and gasket matched the intake runner. I will be polishing the exhaust side as best I can. I will likely polish the chambers as well. Oh also, if you disassemble a set of these heads and run your finger along the "top" of the intake runner, where it meets the valve seat is a big lip. I smoothed that out so air can freely flow along the top and right into the cylinder (since air going in and out of the engine follows the roof of the port) .