The present exhaust in the head can be made larger. After moving the seating area to a larger diameter, some grinding in the port bowl would be beneficial however, not necessary.I searched the forum and still could not find a good answer to my question. I have a set of emission D3VE heads off an 1986 truck 460. I am pretty sure they have hardened exaust valve seats. What is the work required to install a larger exaust valve? (1.72 or 1.76) Do I need to go to summit and get larger seats and have the machine shop press the new seats in?