Porting iron heads can be fun and rewarding. I would only do a set that have healthy guides and valves-seats and such so minimum money will be invested.(Duh right?) I have done a set of 360 J heads Im quite proud of. I have no flow numbers but I had the time the tools and motivation. Im no Steve Dulcich- his J heads showed MAJOR improvement over stock. Practicing caution My goal was not to make things 351 Cleveland 4bbl bigger but to blend and remove lumps slag and feather seams. Just by doing this actually enlarges things noticeably. It was fun and I have no worries about ruining flow as some home port jobs do. I left what the factory designed just smoothed it all out very nicely. I removed just a little from the pushrod pinch. Gasket matched intake ports and bowls and left them rough from cartridge rolls. Int and Exh valve guides were rounded and tear dropped at their square edges-. Nothing like what Mr Dulcich or other pros do ( he knows how much is safe to remove) as he removed a lot of structural mass. Chambers have a nice mild polish as do the exh bowls and ports. It was quite fun although Id only do this for myself as it took many many hours and the rotary tool numbs my hands.