Hardened valve seats - do they really matter?

volaredon said

When it comes to cars and trucks (at least my own) and engine work I'm almost never "not" working on something from Mopar. The same machine shop mentioned above has told me more than once that Chrysler couldn't do a concentric valve seat if their lives depend on it. Almost every one he gets in is eccentric to start with...

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That machine shop sounds like they can't get the guides on center. All the MOPAR valve jobs, I've done the seats were pretty concentric. I used to have a guy grind my valves and seats, who blamed Amoco gas for his valve jobs not lasting. My cousin Kelly's dad had a shop in the same small town. One day Kelly told me Marvin's valve grinder was shot. When I looked incredulous, he said to just lap the valves on one of Marvin's valve jobs. Wow! It looked like saw teeth on the valve face. Kelly did my valve jobs from then on, till I got my own valve grinder. I still lap a couple valves to check seal and position on the valve face. As to the original question, I prefer stainless exhaust valves to hardened seats. I feel it keeps the centers better than trying to keep the guide, seat, and now the hard seat on the same center.