Hardened Seats for Big Block Heads

[71-440-Duster]

Does anyone know when or what heads have hardened seats from the factory?

I have a set of 213 heads off a motor home and the casting date of the block is 1973 and wanted to know if I need to run with a fuel additive or not to protect these things.

Thanks in advance...

 

[Mrmopartech]

The you talk abot is a 3751213 head with 2.08&1.74 valves.these heads are found on the 400&440 motor home only motors.The heads with harden seat s started in 1973 with flame harded seats,not inserts.Mrmopartech

 

[71-440-Duster]

I guess I will save the fuel additive for my 71 440 Charger...