HARDENED VALVE SEATS

marlinjackThe Machinist #5723 AMARGOSA MACHINE 'Running on Empty- Middle of Nowhere'

Can anyone say exactly what year ford started installing/providing hardened valve seats in preparation for burning unleaded gasoline? Was it 1975, or later? If so, I am assuming all of our original clevelands are without them! So my point is: Do the valves eventually "sink" into the seat? If so, how many miles can one expect to get before this starts to really effect performance?(counting ONLY the miles that UNLEADED fuel was burned). Is it both the intake and the exhaust valves, that are affected, or just the exhaust? And last, when I do have my heads rebuilt, I have been told that I need only install hardened seats under the exhaust valves only; is this true?? Thank-You very much for your time! Marlin.

9/8/021:20 PM

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