Wade Keene
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It was '75 or'76. Machine shops put in hardened unleaded valve seats as a matter of course anymore, and I would they have for years. If a '74 has had headwork in the past X years since leaded became unavailable, I wouldn't worry about it. Even if it hasn't I still wouldn't worry about it, the extra wear is a slow occurence. As I understand it, valve seat recession is the problem and the cast iron that slowly recedes is the area that gets milled out to put in a new seat anyway.