Nailhead valve seats ?

[35chevcoupe]

I dropped of my cylinder heads at the machine shop and he asked me about hardened seats , but I thought I read somewhere that installing new seats was risky because the coolant passage was pretty close .
So wondering what everyone is doing , are we running fuel additive ( lead substitute ) or having hardened seats put in ?
Or are these heads fine just the way they are .

[Dr Frankenbuick]

Should be fine. Very high nickel content and  permeated with lead over the years. 


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[Buick_65]

Don't do hardened seats. Very risky. Have the machine shop check out Russ martins nailhead info on the centerville auto website. Tons of good info and things to avoid.