In automobile class back in the early 80’s, i took apart 2 cylinder heads. One head came off a car that ran on leaded regular fuel. The other, the car ran on unleaded fuel. Upon disassembly, the head that ran the leaded fuel, other than being gunked up with crud, was perfect. I could have literally just cleaned it up and reused everything.
The cylinder head running the unleaded fuel, the exhaust valves were mico pitted. The exhaust valve seats, were just as bad. If not worse. Many of the valve seats, were pounded up into the head. A term called valve seat recession. And the intake valves weren’t much better.
I have no idea of the age and mileage of the cylinder heads i was working on. But i certainly saw the difference in the end result, between a vehicle that ran on leaded fuel, and one that ran on unleaded fuel.
Hopefully in the 40+ years of metallurgical advancements, we’ve come a lot farther. But i don’t want to be the first one to find this out, as an exhaust valve takes it last ride, as I’m climbing out of the departure airport…