They are only hard under the exhaust seat. You can install a variety of seat materials in a head that's not factory hardened.
IMO, any engine over 315 CID (or with a bore size of 3.9 or greater...especially if the valves open on the bore centerline....hint, hint,hint) should have, at a MINIMUM, a 2.02 intake valve.
In fact, a 340, with a 4.04 bore SHOULD have a valve of 2.100 diameter. The problem is...that the port can never be made big enough to support that diameter valve.
Emissions is what drove the 1.88 valve, not low end horsepower.
