time ago there was a discussion about this topic and a couple of guys wrote,
that they never used any hardened seats, used no Pb gas and made well over
100000 miles happily... with no recess of the exhaust seat.
It was a 2 computers before, so I lost the files, but I'm sure about
rgds
MAtt
81CS 468 ( no inserts but some top quality valves )
To survive unleaded gasoline, one *****must***** have separate alloy
steel
hardened valve seats installed in the heads and stainless steel
intake and
exhaust valves.
