Herman Kohnke is right about the proper valve placement or height being important. If you decide to install new valves...An
option to installing intake valve seats would be to install larger (or up to 1.73") intake valves. The machining required at the block for most larger valves will get you into fresh metal so you would not need hardened seats to raise the valve to proper height. I install larger intake valves almost all the time on rebuilds. I've installed close to 70 sets. The 1.73" valves are available from Antique Engine Rebuilding in Skokie IL. Do a search on his business name if you want to study them. I suggest the one piece guides also...I believe/find they center the valve to the seats machining more closely. If you do install the 1.73" valves make sure you have adequate clearance to the sidewalls of the combustion chambers. An original Ford head has always worked with the larger valves but the later production heads will sometimes need clearancing. If you find the head has a "date tag" on the casting watch out...check it for clearance before installing the head! It is easy to clearance the chamber with a die grinder and carbide burr. Snyder's HC heads work with no modifications.
UPDATE: When the 1.73" valves are installed, I open up the intake port below the valve seat and blend the bottom to smooth out the transition. I find the larger valves add 1-2 HP in the dyno tests I have completed...even more when using an enlarged A manifold (or B manifold) with a "B" carb. The extra HP is only evident at the higher rpm portions of the tests. (2000-2400)
Good Day!
Dave in MN
www.durableperformance.net