Early engine Q - head inserts?

Hello,
I am wondering why many of the early engine rebuilds include the recommended step of installing hardened valve seats in the head. Is this a critical step? Years apart but both bred on leaded fuel my '79 Laverda Jota & my '53 Chrysler Hemi are candidates for this treatment.

Given the amount of leaded fuel mills out there on the HAMB I would expect everyone to have gone through this ... or not ... flatheads, nailheads, etc.

Any ideas?

Thanks,
papa al

PS I am motivated by curiosity & wanting to skip this step to save some $$

 

the exaust valve is the hottest thing in your engine,the heat is transferred from the valve to the head where that heat is dissipated (hopefully) into the cooling system.hardened seats at the least allow you to go more miles without a valve job,at their most effective you keep from frying valves and hammered seats.for those of you who miss lead,they have since done studies that show it accelerated bore wear.i'd rather do a valve job than yank the engine and get it bored out,new pistons/rings etc.

 

FWIW, Buick nailheads don't need hardened seats, in fact you can ruin a head real easy, trying to install them. The blocks had an unusually high nickel content in the cast iron, so valve recession is not a problem on the nailheads. Trying to fit in hardened inserts, however, is dangerous because it's really easy to go too far and get into the water jacket, rendering the head junk.

Point is, every engine has it's own characteristics and before doing anything out of the ordinary, make sure your shop knows their way around your particular engine.

My 2¢