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If I were you I would disregard any advice you have gotten about not using hardened exhaust valve seats. I have had it happen to me, and I've seen it happen to other heads. It's possible that it may not happen to your set, but to be on the safe side I would go with hardened seats. The factory didn't put hardened seats in the later model heads for nothing.



Exactly what heads have you had it happen to and what kind of vehicle were these heads installed in and it's usage?

The later heads have hard seats partly because of metallurgy change that occured , they changed the blocks so one can only assume the heads were of the same mix?

I'm not saying not to do it , it's money well spent but for a PLEASURE usage vehicle that doesn't get pounded on daily for extended periods it's not a must.